Yeh its pretty normal. You'll pick up 'haters' along the way, its just the way youtube is. Dislikes aren't really a very good way of gauging if your content is good or not anyway as its so easy to just click as soon as you say or do something that someone doesn't like. I wouldn't let it get to you, just concentrate on view numbers, subs, watch times etc. to see what videos are engaging or not.
Also, dislikes don't have an effect on how many people will be able to find your video. They don't push it down a search list, if anything they actually help views by flagging it up as a talked about video.