Imagine living such a hateful life that you have to tear down others who are just trying to live happily. Especially those who aren't hurting anyone.
Silly example to illustrate a point. I personally dislike blue cheese on any dish, especially hamburgers. But I'm not going to walk into a restaurant and tell other people they aren't allowed to have it. I'm gonna think to myself, "Oh, not for me, but you go on and enjoy it!" Their preferences are not harming me or others in any way, and I'm glad they're able to find something that makes them happy, even if it's not to my personal tastes.
It's as simple as minding your own business. There's no reason for happy people to tear down others who are also trying to be happy.