The shirt is using an aggressive tone, which is inferring the person wearing is someone who would complain about “those damn libs and their pronouns.”

But even with the aggressive tone, the shirt is letting us know that which pronouns he uses.

It’s strange that he feels the need to tell everyone they need to deal with the fact that he was born a man and identifies as a man when nobody has a problem with that.

Imagine someone saying “yes, I like pepperoni pizza, deal with it.” Like, uh, okay, it’s one of the most popular pizza ingredients. Extremely uncontroversial opinion, there. Compare that to someone saying something like “yes, I like pineapple and anchovies on my pizza, deal with it.” While it still may be odd/cringey to wear a shirt saying that, it’s at least a controversial opinion.

That man in the image is projecting to everyone the complete opposite of what his whispering subconscious is trying to tell him; the truth is that he is likely very very gay or an uncracked egg envious trans woman, but his dogmatic religious upbringing and close-minded social circles and family would ostracize him for acting on his desires to be overtly gay/trans.