Intolerant tollerance

Why is it when someone wears a pro-life shirt around and people get upset, we are told to be tolerant of their opinions. After all, this is America. We are built on the idea that all opinions have equal weight and value (so they say). If is perfectly acceptable and encouraged to loudly and publicly disagree with almost any socially conservative or traditional values. In fact if you don't disagree with at least a few you are probably going to be labeled as narrow minded and unable to think for yourself.  However, if you choose to disagree with any of the more "progressive" values, like pro-abortion or gay marriage you instantly fall into the same category with an added smattering of the intolerance label thrown on just for good measure. Why is it you can't disagree with a lifestyle someone chooses to live without being looked at as if you are crazy? I find it extremely ironic that the people who scream loudest for tolerance are, in fact, some of the least tolerant people I have ever met.