That is so weak. If a guy drinks a ton of beer, gets drunk and drives home, gets involved in a wreck, are you going to say the beer and the wreck are merely coincidental because he drank water at some time as well?
Mrs. Grundy would be proud.
There's a huge difference.
We can prove a causal relationship between alcohol and poor driving. You take a large group of people and randomly divide them into two groups. Give half of them three beers and the other half three non-alcoholic bev's that taste and smell like beer and let them drive around a track... or drive a simulated car... or use some measure of reflex time and vision. Then look at the results. If the results of the two groups are significantly different, then you've proven a causal relationship. This study (and others like it) has been performed over and over again. There is no longer any doubt that alcohol intake is a cause, not a side effect of, poor driving ability. Nor is there any lingering question that perhaps poor driving ability and alcohol intake both have the same root cause.
As far as I know we've done no similar study with porn... and the "evidence" that porn causes violence presented here would be wholly rejected by anyone with even one semester of college-level statistics.
It could be that doing * and enjoying it tends to cause people to want to relive the moment by watching other people *. Or... it could be that your love of * causes you to both watch other people * and to * yourself. Or it could be that a person believes that most people who do * like to watch * and feels pressure (real or imagined) to watch * by others who like to *.
Or, yes. It's possible that watching * encourages people to actually do * when otherwise they might not have. They're all possibilities. And until proper studies are done, assuming a causal relationship is unfounded.
Replace "*" with whatever you like. Performing music, playing sports, gambling, playing chess... or the obscene (if you prefer).
Say it with me once. Correlation does not imply causation.