I disagree. Your example could be used as a method of suppressing the truth. Suppose I entered a hacking forum and posted "People should value and respect each other and not break into someone else's computer". What do you think is going to be the ratio of dislikes to likes on my comment in that kind of forum? Anyone who has an agenda is going to attempt to suppress the opposing view regardless of its truthfulness.
I do, however, totally agree with your first statement; "Dislike buttons create peer pressure and negative sentiment".. which is why I feel dislike buttons should be avoided altogether.