Hate Bandwagon

It's when someone starts saying they hate something, just because there's a lot of other people who also hate that thing.

For example, if a new video game was released, and a lot of people hated the game, someone might start saying they also hate it, but they only "hate" it because so many other people say they hate the new game. It's like that person is hopping onto a hypothetical "hate bandwagon".