Personally, I think too much porn is obviously unhealthy. It can be an addiction. As a general concept I don't think it's unhealthy per se, especially not in the "do you want to see another guy fucking what you desire" kind of sense, which is just repackaged beta-cuck-whatever bullshit (you could apply that logic to basically all fantasies that are physically possible).
Unless it becomes an addiction I guess it's fine, although porn does distort expectations of what sex and bodies are like in young, inexperienced people. No, kids, sex isn't really like that. You don't have to grunt like you're punching holes into steel with your dick, women's assholes aren't naturally that clean and bleached, and you don't have to be a sword-swallower/yoga-master to be good in bed.
Porn is fine until you lose contact with reality is what I'm saying. Which, with the proliferation of porn thanks to high speed Internet (the causal relationship might be backwards, though; the Internet is for porn, after all), is easier than ever, so this is certainly a new challenge for parents. Do teeny magazines like "Bravo" or equivalents still exist? Those provided some much more realistic sex tips for teenagers (hilarious for adults and kids today, but it was all we had back then)...