Ask Lemmygrad

I'm not sure it can really be universalized. It's probably going to be relative to a specific country's conditions and the history of those groups. In the US, for example, democrat and republican at each other's throats is arguably a kind of rightist infighting, but the mass public perception of what left and right is, is so confined and erasing of anything anti-capitalist/anti-imperialist/anti-colonial that you have people genuinely thinking democrats are left and republicans are right. In the spheres of like, actual "left" in the US, there's clearly some infighting, but I don't think it tends to get all that visceral beyond debating and group splitting because there's no real political power of violence to exercise in the first place.

But then like, the "two parties" don't seem to (so far) get violent with each other either, probably because the actual institutions at the highest levels are more or less on the same side. It's more the voter level of things where people view it as a huge ideological divide.

And that's just one country example in a rough analysis, which could probably be gotten into in a lot more detail over the history of it, like if we include FDR-era reformists and that sort of thing.