I rarely talk about this because I am in a same-sex marriage, so people tend to be very blaming. But my son is five, and he definitely clearly rejects many thing about being a boy. He is not angry like your little one, but he does seem to me to be sad about societal expectations for him as a boy.
He is a sweet, gentle little soul, and he definitely notices when people say things like "boys will be boys," and "rough and tumble" and all that. He adores pink and glittery! He carries chapstick around like lipstick.
His best friends are girls. In fact, there aren't too many boys he likes except for a couple of cousins. He likes things neat and beautiful, and his last birthday party was a "flower party," according to his theme choice. 90% of the kids he invited were girls.
We have lots of strong adult men role models in our kids lives (our kids are very close with their grandparents, for example...spending tons and tons of time at their house, and they also have a close relationship with aunts AND uncles, with whom they also spend a lot of time). My daughter is drawn to her uncles and grandpa like a magnet, but my son wants almost nothing to do with them.
My son likes trucks and things okay, but he also loves dolls. He really wants to take a dance class, specifically ballet, but he also says that he never will because he is afraid he will be jealous of the girls who will get to wear tutus and things to performances.
He is relatively patient in wearing unisex and boy things when out of the house (having parented an older transgender foster child, we realized how important it was to teach a gender-bending boy some safety tools), but when we are at the house, well, let's just say he has taken over all the dresses in my dd's closet. He wears his hair long because, he says, it is prettier.
When he plays make-believe, he tends to choose girl characters. When my kids play house, they usually pretend there is a mom and a dad, but my son always asks my dd to pretend she is the dad so he can be the mom. The other day, when I told him I was writing a letter to someone named Stacey [nice last name], he paused and said thoughtfully, "That is a BEAUTIFUL name mama. I think I might change my name to Stacey [nice last name]."
It is hard to watch him feel sad about this stuff. One painful moment in time was an issue with slippers at school. All the kids were required to have slippers. So my son picked out these cute little pink slippers...very girly.
I tried to be supportive, but also wanting to prepare him just in case it was an issue with some of his classmates, I said, "Some people think these slippers are only for girls. A lot of people don't think so, and I don't think so, but some of the other kids in your class might think so. Do you want some help planning what you might do if they say something?"
Well, that freaked him out, and a week or so into school I found out he had been refusing to wear his slippers. I felt awful. So we gave him other slippers to wear, but he didn't want to
not wear the pink slippers. So he sort of became immobile because he wanted to wear the pink but didn't feel confident to do so. And he struggled and struggled with it, and I could tell it really made him sad, and it never did fully get sorted out.
Another really hard moment was when this spring, one of the little girls from his class, who he *adores* told him that she was having an all-girls birthday party so he definitely wouldn't be invited. This is a kid my ds talked about non-stop all year. This really hurt him. It makes me want to cry just thinking about it.
Anyway, I think at six it could definitely be a phase. No way to know. That said, I have a tomboyish dd, but I see a lot of differences between her relationship to her gender and the way ds is about his gender. For dd, it definitely seems more like a personality/phase thing that goes skin deep. She just lives at odds with certain gender stereotypes.
For ds, there is something more fundamental there. I don't think he is transgender (who knows, but I don't *think* so), but I do think there is something about the societal boy identity and his identity that are at fundamental odds. It is probably not phase-y for him, and definitely not skin deep. It just feels palpably different to me.
I just wanted to write to say you are not alone.
(By the way, your post reminded me of my friend
Lian, who definitely was angry as a kid about being a girl.)