The worst fear of edgy /pol/faced rightoids is being mocked as impotent.
They're immunized against most insults; ugly, fat, evil, monstrous, degenerate - even failsons. They can shrug it all off.
The /pol/face meme on the other hand acts on their deepest fears. Their pathological sense of inadequacy, impotence and fear of emasculation that informs their worldview.

It's okay to be ugly, undesirable, even a cum-guzzling diaper-scat bottom-furry. As long as - deep down - they're feared.
They're okay with being ignored, denounced, even mocked. But they can't stand being laughed at as impotent and powerless. It's many times worse than being ignored or mocked in other ways.
It's like the incel fear that women will laugh at them. It's not the rejection itself, it's having their deep seated self-loathing and impotence publicly acknowledged by the Other.
Specifically: The fear of being perceived as powerless is greater than the actual fear of being powerless.

Liberals of course play right into this by portraying rightoids (including /pol/faced mass shooters) as a terrifying unstoppable evil that should be feared by the masses. Something they get off to. Every. Time.

/pol/ has been mocked for years, going back to the 7+1chan days. So far nothing stuck. Leaders exposed as zionists and pedophiles? Nothing. Furries and Nazis in drag? Nothing. Hypocrisy? Statistics? Actually existing white genocide by rightoids? Nothing.

The /pol/face though made them melt down within 24 hours. To be the point they've spend days spamming with thousands of IPs to prove how "not mad" they are. (Mind that they've never done this before)

And before you say "words words words" or "da left cant meeem" here's a TLDR: You're impotent, inadequate, powerless. And deep down you know it.