Rattlesnake Christians

As for practices being ok, I would say that they have to be supported biblically as well as applicable to modern times.

I'd say that safely rules out any religious practice

Check this out..

http://www.davidicke.net/religiousfrauds/pentecostal/snakeskill-fool.html

Okay, that makes sense. So this could boil down to a literal misinterpretation of scripture.

I also found this passage from a very popular book.

"And these signs will follow those who believe: In My name they will cast out demons; they will speak with new tongues; they will take up serpents; and if they drink anything deadly, it will by no means hurt them; they will lay hands on the sick, and they will recover"
(Mark 16:17-1

[They shall take up serpents] When it is necessary for the sake of establishing religion, they shall handle poisonous reptiles without injury, thus showing that God was with them to keep them from harm. This was literally fulfilled when Paul shook the viper from his hand. See Acts 28:5-6.
[Any deadly thing] Any poison usually causing death.
[Shall not hurt them] There is a similar promise in Isaiah 43:2.
[They shall lay hands on the sick ...] See instances of this in the Acts of the Apostles, Acts 3:6-7; 5:15, etc.

[Take up serpents] Several MSS. add en tais chersin, in their hands-shall be enabled to give, when such a proof may be serviceable to the cause of truth, this evidence of their being continually under the power and protection of God, and that all nature is subject to him. This also was literally fulfilled in the case of Paul, Acts 28:5.

[If they drink any deadly thing] Thanasimon (pharmakon) being understood-if they should through mistake, or accident, drink any poisonous matter, their constant preserver will take care that it shall not injure them. See a similar promise, Isaiah 43:2.

[They shall lay hands on the sick] And I will convey a healing power by their hands, so that the sick shall recover, and men shall see that these are sent and acknowledged by the Most High. Several instances of this kind are found in the Acts of the Apostles.

That the apostles of our Lord should not lose their lives by poison is most fully asserted in this verse, and there is neither record nor tradition to disprove this. But it is worthy of remark, that Mohammed, who styled himself THE APOSTLE OF GOD, lost his life by poison; and had he been a true apostle of God, he could not have fallen by it. Al Kodai, Abul Feda, and Al Janabi, give the following account.

When Mohammed, in the seventh year of the Hejra, A.D. 628 AD, had taken the city of Kheebar, from the Arab Jews, he took up his lodgings at the house of Hareth, the father of Marhab the Jewish general, who had been slain at the taking of the city by Alee, the son-in-law of Mohammed. Zeenab the daughter of Hareth, who was appointed to dress the prophet's dinner, to avenge the fall of her people, and the death of her brother, put poison in a roasted lamb which was provided for the occasion. Bashar, one of his companions, falling on too hastily, fell dead on the spot. Mohammed had only chewed one mouthful, but had not swallowed it: though, on perceiving that it was poisoned, he immediately spat it out, yet he had swallowed a sufficiency of the juice to lay the foundation of his death; though this did not take place until about three years after: but that it was the cause of his death then, his dying words related by Al Janabi, and others, sufficiently testify. When the mother of Bashar came to see him in his dying agonies, he thus addressed her: "O mother of Bashar, I now feel the veins of my heart bursting through the poison of that morsel which I ate with thy son at Kheebar."

Abul Feda, Ebnol Athir, and Ebn Phares say, that the prophet acknowledged on his death-bed, that the poison which he had taken at Kheebar had tormented him from that time until then, notwithstanding blisters were applied to his shoulders, and everything done in the beginning to prevent its effects. Al Kodai and Al Janabi relate, that when Zeenab was questioned why she did this, she answered to this effect: "I said in my heart, If he be a king, we shall hereby be freed from his tyranny; and if he be a prophet, he will easily perceive it, and consequently receive no injury." To support his credit, he pretended that the lamb spoke to him, and said that it was infected with poison! See Elmakin, p. 8. It was therefore policy in him not to put Zeenab to death. It has pleased God that this fact should be acknowledged by the dying breath of this scourge of the earth; and that several of even the most partial Mohammedan historians should relate it! And, thus attested, it stands for the complete and everlasting refutation of his pretensions to the prophetic spirit and mission. Vide Specimen Hist. Arabum, a POCOCKIO, p. 189, 190. Le Coran traduit par SAVARY, vol. 1 p. 135, and 212. See also, The Life of Mohammed by PRIDEAUX, 93, 101.

If they drink any deadly thing - But not by their own choice. God never calls us to try any such experiments.

They shall take up serpents (opheis arousin). Jesus had said something like this in Luk_10:19 and Paul was unharmed by the serpent in Malta (Act_28:3.).

If they drink any deadly thing (k'an thanasimon ti piōsin). This is the only N.T. instance of the old Greek word thanasimos (deadly). Jam_3:8 has thanatēphoros, deathbearing. Bruce considers these verses in Mark “a great lapse from the high level of Matthew’s version of the farewell words of Jesus” and holds that “taking up venomous serpents and drinking deadly poison seem to introduce us into the twilight of apocryphal story.” The great doubt concerning the genuineness of these verses (fairly conclusive proof against them in my opinion) renders it unwise to take these verses as the foundation for doctrine or practice unless supported by other and genuine portions of the N.T.

shall take: Gen_3:15; Psa_91:13; Luk_10:19; Act_28:3-6; Rom_16:20
It is fully asserted here, that the apostles of our Lord should not lose their life by poison, and there is neither record nor tradition to disprove it. But it is worthy of remark, that Mohammed, who styled himself the apostle of God, lost his life by poison; and, had he been a true prophet, or a true apostle of God, he would not have fallen into the snare. 2Ki_4:39-41

they shall lay: Act_3:6-8, Act_3:12, Act_3:16, Act_4:10,Act_4:22, Act_4:30, Act_5:15, Act_5:16, Act_9:17, Act_9:18, Act_9:34, Act_9:40-42, Act_19:12; Act_28:8, Act_28:9; 1Co_12:9; Jam_5:14, Jam_5:15