It's not the peoples fault to a large degree. We are brought up to be offended by things we are taught are wrong. If I saw a T-Shirt that said "I saw Jesus fuck a dead baby!" I personally wouldn't be offended because I have no emotional investment in the subject matter. I'm sure alot of others would be horribly offended by the shirt though.
America, it seems far moreso than the UK seems to be trying to cling on to the insanely puritan values that the people we kicked out for being "insanely puritan" founded the country apon. A decent percentage of people still hold those views to a greater or lesser degree, so things which are perfectly acceptable in Europe or other places are still seen as taboo.
Seeing a cop shoot at a bad guy in a film is fine in America because it's an accepted part of everyday life, seeing an unmarried couple get it on in the back of a car is incredibly bad (unless the killer then punishes them for their wicked ways, teaching the audience that if you're promiscuous YOUR GONNA DIE!). On the reverse, we're quite fine to see people do the deed, yet we're more concerned with violence.
Then we come on to the people that get offended by the little things. Some of the things people get offended by, even on this site are hillarious. Justin Bieber for example seems to offend so many simply because he exists?
I'm rambling now, I've been away for a week so I haven't had my daily fix of typing shit, so Ill answer the question. Yes, people get offended far to easily these days, although I'm guessing it's no different from "the old days" we're just more aware of it now because we're living it.