Greg Koukl writes helpfully about tolerance:
If you’re placed in a situation where you suspect your convictions will be labeled intolerant, bigoted, narrow-minded, and judgmental, turn the tables. When someone asks for your personal views about a moral issue, preface your remarks with a question.
You say: “You know, this is actually a very personal question you’re asking, and I’d be glad to answer. But before I do, I want to know if you consider yourself a tolerant person or an intolerant person. Is it safe to give my opinion, or are you going to judge me for my point of view? Do you respect diverse ideas, or do you condemn others for convictions that differ from yours?” Let them answer. If they say they’re tolerant (which they probably will), then when you give your point of view it’s going to be very difficult for them to call you intolerant or judgmental without looking guilty, too.
This response capitalizes on the fact that there’s no morally neutral ground. Everybody has a point of view they think is right and everybody judges at some point or another. The Christian gets pigeon-holed as the judgmental one, but everyone else is judging, too. It’s an inescapable consequence of believing in any kind of morality.
I would highly recommend Greg’s book that will help you think through this type of conversation and many others.