Much like "paradigm" and "pro-active" in past times (Simpsons reference, anyone?), "tolerance" has become a buzzword in our society, a sacred sound invoked by people to communicate to others that they have the correct mindset, the proper disposition, the right attitude. "We need to work toward a more tolerant society," they'll say, hitting that T and exhaling on that O to milk the word for all its worth.
But I must say to such folk, in the words of Inigo Montoya: "You keep using that word; I do not think it means what you think it means."
The above-mentioned sort of person tends to use "tolerance" as a synonym for "acceptance." When they say we should "tolerate" a particular behavior or idea, what they usually mean is that we should accept it as a legitimate behavior or idea, that we should welcome it into the fold of The Normal, that we should strive for the day when we the practice or idea is approved by society as laudable and admirable. That is acceptance. That is not tolerance.
To tolerate something is to precisely say, "I think this is wrong/stupid/worthless, but I will allow your practice/promotion of it, because you have a right to your opinions/practices." To say that you tolerate something is not to say you approve of it; it is precisely to say that you disapprove of it, but that you will allow it over your objections. You don't tolerate something you find to be good or acceptable.
(Please do not attempt to contradict me by pointing to dictionaries or thesauruses that list "tolerance" and "acceptance" as synonyms. Dictionaries and thesauruses tend to follow usage just as much as they dictate it; if a mistake in grammar or definition is made often enough, dictionaries will start to list them as "alternate usages." J.R.R. Tolkien, who worked for the Oxford English Dictionary, often complained of this phenomenon. These two words have different definitions that allow us to make a useful distinction. Let's not paper over them.)
We see this word used quite often today in the debate over same-sex marriage. We are told we ought to be "tolerant" of people of homosexual orientations, but such advocates typically actually mean we should be "accepting." (And they do sometimes use that word, to their credit--at least then they're saying what they mean.) Now, if we were to use these words properly, "tolerance" would translate in public policy to "not using legal force to punish homosexual acts with fines or jail time," while "acceptance" would be more akin to "redefining marriage so that it includes this arrangement." Those are two very different things. Tolerance can be mapped onto the Church's notion of "love the sinner, hate the sin." But acceptance would have us call a sinful act good. That is not acceptable, nor will I tolerate it.