So reactionaries have a flawed association between certain types of dogs and what they represent.

(X breed) are more badass, they're more violent, they're more masculine, they're more acceptable for a man to own, they're more loyal, etc. Unfounded associations, ofc.

Bulldogs (esp French bulldogs) were a lot more bourgeois than they are now. They were associated with bloodsports, yes, which earned them a certain reputation for being a masculine fightin' dog. But it was more likely due to them being smaller (but not too small) and cheaper to feed for said bloodsports while also having a shorter snout, compared to something like a borzoi which would have been detrimental to fighting.

Aforementioned reactionaries seek out those particular breeds associated with violence and machismo and whatever.

Said reactionaries are reactionaries, and are therefore bad at raising dogs.

Said dogs are neglected, not trained or actively trained to be aggressive

Said dogs get the blame for their behaviour if something bad happens and not the humans that created it. After all, they're already associated with violence!

Said breeds are strong enough to cause severe damage IF they act out, which gets reported.

Future reactionaries continue the trend.

It's a feedback loop. Within pop culture, the established "violent" breeds are depicted as violent. It's not a poodle that's attacking strangers in the street. """Smarter""" dog owners are turned away because the "violent" breeds are less safe! Which in turn boosts the desirability of those "violent" breeds to future reactionaries. A shitty dog owner's dog mauls someone? Don't self crit, blame it on the dog. Others see and are like "oh shit! That's what I need, a badass dog because I'm a badass". Gets said dog, ends up being a terrible owner. Ad infinitum.