Because they know you will spill your heart out on forums. On line people are different, everyone can be a MMA fighter behind a keyboard. But in reality no one is.MMA fighters has nothing to prove (neither does anyone in a fighting branch of a military, law enforcement and the like). So they won't bother talking smack to a regular person. They don't take the time out of their day to do something insignificant like that.
If you let a dislike affect you I fear for your future. I ignore them. They are not worth my time. There is enough negativity around to let myself be affected by something as silly as a troll disliking my video. Thanks for the +1 view and +1 engagement on my video kind troll, now scurry along and find Toridori, he'll give you the reaction you need for your infantile troll brain.