[dude with glasses in a communist t-shirt, arguing] I'm the only leftist here, your opinions are TRASH
[dude holding a theory book on smug, arguing] Read theory you losers, you're all WRONG
[dude in an anarchist hoodie, arguing] Nuh-uh, I'm the only leftist here, you're SHITLIBS
[the three dudes are now caught in a cartoon fight, glasses gone flying, punches everywhere, while a firing squad of nazis are targeting them with rifles]
[a confused nazi asks] Why… why are they still arguing?
The idea that all "leftists" should just work together is stupid.
Leninism, Anarcho-primitivism and Social democracy (for example) are not different approaches to "leftism" that ultimately want the same things; they are completely separate ideologies that naturally come into conflict. The people who follow them disagree with each other because they want and value completely different things. If they were to put aside their differences there would be nothing left.
That doesn't mean arguing on the internet about ideology is meaningful, or that there can't be common goals or enemies, just that you should give up the idea that all "leftists" are somehow natural allies, because it doesn't make any sense.
I believe you are missing the forest for the trees. First, I acknowledge your examples are separate ideologies.
That concept also applies to the right... social conservatives, right-libertarians, and neoliberal ideologies are equally separate. However, those practitioners have no qualms about banding together to suppress dissent (or until such time they are the only voices).
Where the left leaning practitioners are unable to do so, they will be forever tyrannized by the banded majority.
To put it more succinctly, the enemy of my enemy is my friend (when freedom is on the line).
It does help that the overarching theme of the right is centered around taking as much for yourself as possible and not caring about the collateral damage. The right is full of single-issue voters who might, say, not actually explicitly hate gay people but who also don’t give a shit about their rights and safety if it means they can keep their guns. The left, almost definitionally, needs to consider the complexity inherent in not being able to ignore the effects that any given policy might have on others and this means that there is so much more opportunity for conflict.
You’re correct, of course, I’m just pointing out the difference such that it might help attack the issue from a better perspective.
There's the nuance the original post relies on ignoring. But it's supposed to be a humorous joke-post anyway.