DS1 started dancing aged 3, because I wanted him to learn the balance, coordination and body discipline that goes with it. He started with tap and then quickly included ballet, jazz and modern. He has the option now of doing hip-hop but prefers not to.
He's now coming up to 8yo, and this year, Y2 and aged 7, is the first time he's experienced any negativity from the boys in his class at school. They are also in his out-of-school soccer team, and told him boys aren't supposed to do ballet. I told him that ballet makes him stronger and more co-ordinated - but also that dancing was good for football players so they can all just mind their business. I also got him to tell his school teacher which boys had said it, and there has been no recurrence since (very strong anti-bulling policy in DS1's primary school)
DS2 has just started - he's also 3 (but was 2 1/2 when he started).
When DS1 started, some of the older girls in his class were a bit off with him (class was pre-school age, so 3-5) but now, they're no problem. I think partly because they're used to him being there, but also because he quite frequently has a pivotal role in the dance AS the only boy. He's not the only boy in tap, there are 2 others; but he is the only boy in ballet, jazz and modern.
DS2 started being 1 of 3 in his dance class, but the other 2 boys have dropped out - 1 because although he apparently enjoyed it, he never moved; and the other due to family reasons. DS2 doesn't care and all the girls in his class are fine with him, maybe because they were all younger when they started?
I think the only thing you can do is try it and see; but also give him the understanding that dancers are some of the strongest athletes around.