Not OK for workwear, obviously.
Out of work, it's just twattish - I wouldn't be offended by it particularly, but I'd definitely think the wearer was a bit of a saddo.
I have a Cradle of Filth t-shirt (bought by dh) that, frankly, I'll never be able to wear in public, because the slogan incorporates sexual swear words in a context calculated to upset religious people (it's slightly more subtle than the Tool one. But not much.)
I like the band & the t-shirt makes me smirk to myself, but I save it for wearing in bed on cold winter nights.
It's not that I'm particularly averse to being rude about religion, if someone wants to have that conversation, but I wouldn't wear anything publically that goes out of its way to cause unprovoked offence: it's just unnecessarily rude.
I wouldn't bother complaining about the t-shirt in the OP, though - I'd just assume that the lad in question knew no better. Not my job to set him straight.