Nobody's going to throw a fit; I don't think anyone ever said that. However, it still makes the website less enjoyable to users who make a not-so-popular topic. There's not even any pros to having a like system that come to my mind right now.
And comparing to YouTube is a bad argument for a couple of reasons:
1. Youtube uses a like to dislike ratio bar. Sure, the actual amount of likes or dislikes shows, but no one actually looks at that; it's the colored bar that matters.
2. YouTube uses a like system to recommend the quality of the video beforehand. It the dislikes outweigh the likes (or even if it comes half-and-half), viewers will probably be less likely to watch it. But what is the point here? To "recommend" some topics and "deter" others? YouTube's like system would be useless without dislikes, and dislikes are something that will only cause problems for our community.
3. YouTube has a massive amount of users. Seriously, take any two active channels, ask if they know each other, and the chances of them actually knowing each other is basically zero. Most channels have maybe one or two likes not because they are terrible, but because it's impossible to watch every single video (which would take you 60,000 years). Because of this, not having likes won't make you really feel bad. We, on the other hand, have a pretty close community. Most active users probably know each other; we don't have 60,000 years' worth of topics, so they'll be read by most people. At this point, you can see how likes go from being a simple indicator of the video (topic)'s quality to something completely unnecessary that will create competition at its worst and absolutely nothing at its best, as far as I can see.