Trotskyism is a thing.
They hate Trots, these ones are Stalinists, it's what "Marxist-Leninist" means in their lingo. Note that there's both anti and pro-Chinese Stalinists, but anyway they're all positions based on stuff that happened a century ago, not relevant anymore today.
The important thing to know is that the only real difference between modern Stalinists and modern Trots is that the former are slightly less likely to be child molesters or generally sexual degenerates, but they're in almost all cases enablers of this. Even outside of this, their parties work very similarly, and will likely have similar partners as well. The differences you see are largely aesthetic, and the hatred, while intense, is probably even less substantial than the one between a Democrat and a Republican.
At least when it comes to Dems and Republicans we're talking about people supporting two extremely similar parties but into which the electorate will project starkly different ideas of what the country will look like under them.
Stalinists and Trots have very similar ideas of what the outcome should be.