You know what? As painful as it is to admit, I think that's true.
If nothing else, 'only praises are socially acceptable' is definitely an accurate statement. But honestly, it's not just for art-- in any situation where someone is just existing in a public space, minding their business, it's considered impolite to approach them with criticisms if you don't know them.
You wouldn't walk up to a stranger on the street and say "your outfit looks awful-- here's some ways I think you could improve it"...we consider social media posts to be a similar thing. A creator displaying their artwork is just a stranger on a virtual street; what right do you have to start criticizing them, as if they should value the opinion of some rando? That's the thought process, I think.
There's nuance, of course: it's a lot more socially acceptable to intervene if, say, a stranger is wearing something that may be dangerous for them (e.g. their pants are so tight you can see their ankles turning blue)...in essence, if they are somehow unaware that they desperately need help.
Which is unfortunately a lot more subjective in the art world...critics' definitions of 'unaware' and 'desperately need help' are varied, biased, and sometimes completely baseless...and if you think you're the exception (as many internet denizens do...) then you're part of the problem. =/ Honestly, if the 'danger' of posting criticism will prompt potential critics to at least think a little more before they type, I feel like that's a net gain.
It mostly depends on what you said (and how you said it)...but based on everything I just said, it's a good bet that you made some people uncomfortable at the very least.
I think that's definitely enough. Something that also helps is creating a critique-friendly environment with your responses: like explaining how you used what you learned from a previous critique in a new piece of art, or refraining from counter-analyzing the critiques that are given to you (90% of the time the best response to give to a bad critique is radio silence...at best, they just have no idea what they're talking about; at worst, they are actively malicious/judgmental and would love to get into a fight with you).