Why is it acceptable to be a tomboy and not so much for a man to be sensitive? I suppose it has to do with the way we're raised.
Some people prefer raising girls as tomboys because parents feel they have less of a chance with dealing with a girl's natural sexual nature and therefore the girl will have less of a chance to get pregnant because they're not going to have "slut potential" when they get older. However, some of the most gorgeous girls in the world when they're older happened to be tomboys at a young age. They often played sports and enjoyed it so therefore they know how to work out and be healthy that way, as well, they know how to be who they are and are confident with themselves. Sometimes they get sick of being just "one of the guys" and do a complete 360 when it comes to the looks department and they eventually try looking girly and all that.
If a boy is sensitive, it's fine for the mom, but the dad often has a problem with that because the boy isn't asserting himself or being dominant with the opposite gender and therefore will never procreate. This is fine if the mom still wants to baby their son and turn him into a "momma's boy" but to the father in a two-parent home it spells trouble and a lifetime ahead of rejection after rejection of the opposite sex which in turn creates self-esteem issues and heartache.
The way I see it, if you're a tomboy for life though it's because you enjoy everything that world has to offer. I've had the occasional comment that I'm "too pretty to be a tomboy" from random people at conventions I go to. To be honest I wasn't always tomboyish in nature right off the bat. To be truthful when I was really young about 2 or 3 I wanted to be a ballerina, my favorite colours were pink and purple and I adored unicorns or anything that resembled a horse. To be fair I still like some of those things but I'm not as into those things as I was at the age of three. At 5 I wore frilly dresses and my hair was super curly and I loved My Little Ponies, however instead of sitting in the front row with the girls who braided each others hair while the teacher read us books and showed us pictures, I would be in the back with the boys making fart jokes and whispering obscene things about poop.
Later I discovered Ninja Turtles and even faked doing karate moves, imitating the shelled creatures I loved to watch after school. When I got to my awkward adolescent phase I wore baggy shirts (some of which I took from my older brother's drawer that he left behind when he went to University) and jeans with holes in the knees. I didn't wear make-up, hell I didn't care. I refused to tell anyone who I had a crush on in school for fear the guy would find out and be repulsed by the notion that an ugly tomboy would remotely like him. When I didn't tell people about my crushes I was called a lesbian because of how I looked and my too secretive nature. I opted to eventually reveal my celeb crushes because no one would let them know how I felt.
In High School there were a lot of guys around my locker. Some of which were very nice and not bad to look at. It wasn't until I saw a horrible photo of myself that was mandatory for us to get on picture day that I realized how hideous I have become. I eventually bought more girly clothes and started to experiment with make-up. It wasn't until the end of high school that I had my first boyfriend and I admit I wasn't really ready for it then, especially since I was alone my whole life up into that point in time. When I got to college I still looked fairly girly and even ended up being annoying in relationships doing things I know guys hate like pouting to get my way and raising my voice an octave higher to put on a cutesy baby voice that I know now makes guys shudder. I realized I wasn't being true to who I was by acting this way, I was just giving into how girls think they should act and be. I eventually went back to my tomboyish ways and hung out with guys and rather liked it. Not that girls aren't fun to hang out with, but guys are more chill and they have a guy code so they'll keep some big secrets of yours if you don't want them to spread the word. To me giving into my tomboyish nature isn't about not caring about what I look like or being mean to people. It's about being chill, being yourself and being confident with who you are naturally and not about what society tells you how you should be.