When was the last time YouTube recommended an ISIS video to you? It doesn't because they make sure it doesn't. Yet why can't I escape recommendations for alt right/white nationalist vids or memes? Young people are being radicalised and we're not doing enough about it. 'It's just memes' is plausable deniability.
I think YouTube makes suggestions based on what you've been watching. I watched like 2 or 3 alt right videos once out of curiosity and I inmediately got a ton more and had to manually tell YouTube I'm not interested.
I imagine if you saw ISIS recruitment videos you'd get a lot more. Same with any other hateful ideology.
At the end of the day, for businesses it's all about making money.