In my mind, part of that is that the rules are getting stricter, so people respect those rules less. Over time, the needle has moved further towards the idea that anyone can be offended by anything anyone else says. Even if it's clear (to the average person) that the speaker meant no harm (or even intended a totally different meaning for the words), the fact that someone is offended means that the speaker is wrong. Professors get sanctioned for using a racist word in a discussion about racism (and sometimes that word in particular).
At some point, people start seeing those rules as ridiculous and no longer respect them (though they may still feel compelled to follow them, for fear of repercussions).