I explained why in the first post. To be friendly and a generally good person. Legality was not a reason given so I'm not sure why you feel that's an argument. In this case, the guy posting the link does have a bad reputation, which is no doubt the reason for the search ranking hit. His deliberate posting and refusal to remove it makes him a bit of an ass.

And "Why" one should not behave as an ass is self evident in my mind. But we may not agree on this as evidenced by your last sentence.