Some of the comments seem neutral - 'Oh. How do you feel about that?' That's neutral and you can either say how you feel or not.
I think you are being (a bit) over sensitive but that is partly because you feel a bit ambiguous or worried about the fact the baby is a boy.
Can I just say that the assumption kids will get on because they are the same sex is probably not true, yes they can get on if they are the same sex but they can also be big rivals - I would imagine!
Re Dh has had nothing but congratulations. Is it the assumption that he has wanted a boy? I think there might be that assumption but you and your dh don' need to listen to that kind of stuff.
I am sorry that these comments aren't helping to reassure you. maybe hanging out with any friends who have boys and girls might help you feel kids are not that different. My son is a bit of a 'boy' at the moment because he doesn't want to use the ladies toilets (with me), and he very much doesn't want to use things that are for girls (e.g. his sisters 'frozen' bed cover). And he loves cars and helicopters etc. But actually many other things are just kid's things.
I am glad you are getting excited about the new arrival. Try and block out those negative comments.
We chose to buy a few items in 'neutral' shades - e.g. a red pushchair or red parasol for a pushchair, instead of pink. In the hope they could be used for both kids, and they were. But I would personally steer clear of too much gender neutral clothing unless that is what your child wants. Sometimes children really want to express themselves in how they dress, even from a young age, and I feel it is better to allow this. Actually, kids often have way too many clothes, we certainly get given lots! We had/have a variety of friends with children older than ours and are often given bags bags of clothing to use from family and friends. Once word gets round you can use extra clothes often people are only too happy to offer some. We also bought lots of clothes and toys at NCT sales and other sales. And clothes can be sold or swapped.
With regard to having a preference for the a sex of your baby, as in I would like a boy or a girl, some people just have it, they have a feeling they want one or other. It is just a thing. It was not something I was proud of, or expected, after years of wanting to be a mum I was surprised I had any feelings of preference, but I did! I never told a soul, not dh or my sister or anyone. Because I knew if I had a boy I would not want anyone feeling sorry for him and like he was second best. And my son is not second best to anyone!
I think once baby is here and in your arms these concerns will melt away but it is still good to think about this and to help yourself to address these thoughts now. I think it is good to think it through and avoid any negative comments. I really like the '..well I was hoping for a kitten..." answer!
Congratulations.