I think a part of the Homestuck fandom sees Dave's reluctance to fight as a sign of him being weak, even if it's used as a joke.
Rose, Dirk, Vriska, and other characters who are at the forefront of action, are simply avoidant of their feelings and able to compartmentalize their fear or self-preservation, while Dave, Jake and Tavros cannot.
Being a good, reckless fighter serves the Narrative well in Homestuck, since the goal is to fight a boss at the end of the game. But we are shown time and again that it does fuck all in the character's personal lives.
Rose, Dirk, Bro, Terezi, Vriska, Equius, Eridan, and Jade, to some degree, have tumultuous relationships (some more than others) that revolve around their inability to be vulnerable and honest.
For Dirk, Bro, and Equius, this is fueled by toxic masculinity, and it's a core aspect of Lord English.
The characters who have a consistent decent emotional life (they are still teenagers after all) are Karkat, John, Dave, Feferi, Kanaya, Roxy and Jane. Not all of them refuse to fight or are bad at it, but it's not their primary way to respond to an obstacle.
Karkat is aggressive, yes, but he never attacks his friends and he airs out every bit of discomfort, which ultimately is what Dave likes about him, compared to the cold silence and dutiful martyrdom of Bro.
John has feelings he has a hard time putting into words, but being raised by a man who cares what he has to say, he still tries, and he receives Vriska's feelings with compassion.
Jake makes exception to this because he is both a bad fighter and unable to put his fear and discomfort aside for the "greater good", like when he refuses to kiss Aranea simply because he doesn't want to. He is supposed to use his incredible power to beat the Condesce, but he doesn't want to, and that makes him "weak" in the eyes of Aranea.
Tavros is also an exception, for the same reason.
As an aside, I hate how this has morphed into some kind of "girls rule, boys drool" mentality in the fandom.
"Dave is so lame while Jade and Rose are so cool" NO!!! Rose and Jade are also lame! Rose gets wasted in front of her date and Jade is a furry! I don't think it's cool to remove what makes them human, actually. I understand the desire to prop up female characters for once, but all it does is recreate the action girl trope.
I think the inability to compartmentalize is seen as a failure in both men and women. When men can't forgo their fear of death and pain in favor of going to war or fighting, they are weak. It's emasculating.
When women can't put aside their feelings in favor of coddling men's, they are whiny and useless.
Homestuck has a habit of inverting the gender of the trope. This is why it's Vriska calling Tavros whiny and useless, not the other way around. This is why it's Vriska calling (Vriska) weak-- okay it's all Vriska, but you get my point.
I can get behind a good "the weak and lame boys vs the aurafarming gigachad girls of Homestuck" joke, but ultimately Homestuck is telling you that being a stoic, self-sacrificial hero is NOT a cool thing, and it makes you a bad friend and a bad partner.
