Not all the rings of power were tainted by the One Ring. As has been pointed out the Three were kept hidden from Sauron so that they would not be harmed by the evil of the One. And in fact, the One Ring did turn almost everyone who came in contact with it. Gollum is the obvious epitome of the Ring's power, as he killed Deagol to gain possession of it and was later shunned by all his kind and thus driven away for his how the Ring had changed him. Isildur knew he should destroy the Ring, yet he kept it in a vain attempt to use its power. Bilbo lied about how he gained the Ring, which Gandalf stated was out of character for the hobbit. Boromir never even touched the Ring, yet he too tried to take it by force from Frodo, and thus began the breaking of the Fellowship. Sam knew the burden was too great for him, and turned back. Even Frodo suffered from the Ring's power and in the end succumbed to it.
And I'm not certain how "pure of heart" Gandalf was before his transformation after the his battle with the Balrog. Certainly, if Saruman the White, the head of Gandalf's order, was able to be corrupted with the want of the Ring, the Gandalf must have known that he would not fare nearly as well.
Gandalf and Galadriel each knew that while they would try to use it for good in the end everything they did would come to evil, even with the best of intentions (which certainly Frodo and Sam both had) the Ring was stronger. The best reason for Frodo to take the ring was that he was perhaps the least coruptable, Gandalf, Elrond and Galadriel all knew this from Bilbo, who had the Ring for a long time, yet never did any evil with it (though if he had kept it longer he might have begun to do so).
So Tolkien did an excellent job of establishing the evil that the Ring could do, and had already done. And the fact that Frodo was rather pure in heart and motive meant that he was the best man/hobbit for the job.
Finally, I don't know that there is any support for the claim that hobbits had a beer obsession any more then any other of the races. Hobbits certainly enjoyed the simple things in life (good food, friends, stories and tabacco). But I would hardly say that this constituted an obsession. Frodo and Sam only rarely mention the desire for a nice tankard of beer while travelling through Mordor. And what individual would not reminecse about the easier days when such frivolties were close at hand. I am also not certain about the use of the term "cretin" as it applies to hobbits which from Webster's II means: A deformed idiot. Certainly, Tolkien didn't mention any deformity in Sam, Frodo, Merry, Pippin or Bilbo (and those have the largest body of text describing them. Of course Frodo had a cleft chin, but I believe some people find that to be endearing and even attractive rather then a deformity. Obviously, Kirk Douglas was never referred to in this fashion.
-RobRoy
