Nobody thinks it's "acceptable" in general.

Like if somebody minding their own business, all of a sudden starts getting small dick insults hurled at them the crowd isn't going to cheer.

However, if some dude is being a complete assface and someone insults their dick. Who cares.

Just like people would tend to turn a blind eye to insulting the physical characteristics of some ridiculous Karen.

People post these questions as "in general", when it's not so simple. i.e. I am not remotely offended or outraged as a man that Greta Thurnburg implied Andrew Tate has small dick energy. Which I assume is where this question is stemming from. Since it caused all sorts of men to cry about insulting tiny wee wees.