Is it their fault ? Do they need to get a life or is it the "offenders" fault ?

They're just irritating. Sadly a lot of the world/media today is an oversensitive mess.

take this forum for example, so oversensitive

Nothing.
It's all about how you were raised , sheltered and ultimately your individualistic perception of the world.
You too would be offended by things that to others would seem nonsensical .

If someone makes an anti religion comment , peoples that believe in religion will get offended .
If someone makes an anti gay comment , gay peoples will get offended .

I don't really believe in " offended easily " or "oversensitive"

If you get offended easily, then you're an oversensitive bitch
Unless it's something serious, then it's the offender's fault.

I feel offended by you asking this question.

Nothing. My whole life is constantly one big joke and I can't be friends with people that are over sensitive towards my jokes and actions.