I think this has less to do with what consenting adults are free to get up to in the privacy of the own bedrooms (of which anal sex probably falls towards the less outré end), and more to do with the normalisation of messaging to young people.
Greeting cards are there for everyone to see - uncensored and freely available.
I support any adult's wish to buy this for a friend and see the humour therein.
I can't say I'd be delighted with some impressionable teenage lad coming across it, on the other hand. Certainly not one that might cross paths with my DD.
Also, if anal sex is done correctly - slowly, preparation, lots of lube, safe words, STI checks, consent etc. then it significantly reduces the chance of damage.
Exactly.
Unfortunately, most teenage girls on the receiving end of some spotty lad, keen to get his end away via this particular method, won't have this sort of care and consideration taken of their sexual wellbeing.
It won't even occur to said lad, given the sort of exposure they'll have had to anal sex (read: porn).
I mean, the message is - 'no harm done', right....?
That's the real problem.