Seems like a couple of plausible points there.

And yes, the left have more than their fair share of self-inflicted injuries. In the UK the Labour right-wing (or centre as they style themselves in this oddly shaped party) are more than happy to lose elections if it prevents a left-wing candidate from winning. In the 1987 general election, Labour MP Ken Fields urged voters in neighbouring Wallassey to vote Tory when it looked certain that a left-wing candidate, Lol Duffy would overturn a massive Tory majority. The Labour party actively conspired with local press to whip up a "Marxist Threat". Duffy still came only 279 votes from winning. Then there's the almost unbelievable onslaught against Corbyn, largely driven by the right of the Labour party again. Of course, around the world things have been much worse. If it wasn't so tragic and awful, one might even laugh in disbelief that during the Spanish Civil War, Stalinists on the Republican side were actually attacking and killing fighters on their own side because they were in the wrong factions. 

The right aren't exactly strangers to infighting either, but they have the plain sense to work together when the battle is actually in progress.