Memes

You don't need guns to make a revolution. In fact, guns make the worst type of revolution, one that leads to civil war. So if your type of leftism cares about wellbeing of your fellow humans, you would like to avoid a civil war by all means.
A person having a rifle was a threat to power, when power also meant people with rifles, not anymore. The power will thrive in a civil war scenario

I’m a leftist who doesn’t much care for guns but I’ll use one if I fucking have to.

There are reformist and pacifist leftists too (like democratic socialists, syndicalists, anarcho-pacifists), not that I agree with any of them completely.

Leftism at its simplest definition is just opposing social hierarchy (which right wing ideologies like capitalism, fascism, and monarchism promote) in favor of socialism (which can also include communism, anarchism, and syndicalism).

It's because leftism is so broad with differing methods that many leftists hate each other. If you narrow down the definition of leftist to only your own political beliefs, then there wouldn't be much leftists to hate.