I don't like the obnoxious comments on youtube videos but I am indeed one of those people who see this as an attempt at forcing me to join their crappy (and privacy invading) social network.
Obnoxious and hateful comments are found everywhere that public input is welcomed... new sites, blogs, etc. If comments are too objectionable they are deleted. Youtube uploaders had the option to delete comments.
So no, I don't believe Google is doing this for altruistic reasons.