Candidus said:
I don't understand why you feel the need to tip-toe. If people like that disown you, what have you lost? Only the stigma of being associated with some very horrible people.
If you need them to live that's one thing, go ahead and eat their food and take their money until you don't need them any more. Using bad people to get by is fine. But tolerating and voluntarily remaining close to bad people, who make society worse by acting with discrimination informed by homophobic prejudices?
I'd discard my family for that and piss all over the ashes of those bridges, because my sense of duty and justice is stronger than any love I've ever felt, and my hatred of those who act contrary to the spirit of either is stronger still, no matter what their relation to me.
The more we shun and alienate people whose beliefs are disgusting, the more we isolate their cancer from the public space. As soon as you can put your family behind you, I recommend you do so.
As for challenging their beliefs, if you're determined to try... You obviously understand how fundamental the problem is - views aside, they don't seem too bright (as in poor education), they can't see for themselves the fallaciousness of a slip-slope argument, and I'd wager that although they speak hatefully about homosexuals, they probably *like* and take joy from the judgement they're passing and the sneering they get to do...
I don't think there's anything you can do but keep living differently in THEIR space. Accept homosexuals the way any civilised person accepts basically anyone. Buy a DVD by a homosexual comedian. If you have them among your friends, don't expose them to the beratement of your family, but keep seeing them and don't neglect to mention them when recounting your evenings because you're afraid of a confrontation. Etc etc. Just live like you should, and hide nothing. Be stubborn and brave. They'll either lash out or adjust.
The problem isn't hatred towards the group you support. The problem is hatred. You can't condemn a group for condemning another group, basically.
"I hate you because you hate them."
You don't combat differing opinions with disdain and anger, else you're as bad as them. You share your opinion and attempt to change their mind. If it fails, you move on. The only time you intervene and cease their rights is when they harm people. Simply being homophobic isn't harming homosexuals. If they were to, say, preach on the street corner that gay people are animals that need to be eradicated, then they can be stopped, as they are creating a dangerous environment.
Simply: don't become the thing you dislike. Be a force of love, not hate, and that's the best you can do.