Simple. While not all activities depicted in porn are damaging to all people, some activities can be damaging some people. Doesn't have to be black or white. Make sense?
Do you think that the distortions effects are negative or positive overall now? And in the future? I'd argue they are positive now and in the future, so it sounds like this is where your disagreement is coming from (since you said it as if it's overwhelmingly negative now and into the future).
nope. i can find cases where smiling is not beneficial. Eg: Lookup Angelman syndrome and tell me again how smiling is beneficial to parents that have a kid with this disease.