If user attention is split between Twitch and Youtube then they are a competitor. Same for Netflix. Same for Pornhub. Same for Vine when that was a thing. But

If user attention is split between Twitch and Youtube then they are a competitor. Same for Netflix. Same for Pornhub. Same for Vine when that was a thing. But if you focus attention to political commentary specifically, then YouTube is clearly the dominant giant. In that context, they are a defacto monopoly.