You're definitely not being unreasonable.
Parenthood isn't for everyone and there's absolutely nothing wrong, in my book, with saying "Nope, not for me, thanks". I grew up never being remotely interested in having kids but had a brief period around 30 where I was considering the idea, which co-incided with being in a relationship with someone who very much did want kids. But my feelings never went beyond 'maybe but probably not' and we split because of it. I'm happily child-free now at nearly 40, and I can't imagine that changing.
I've heard quite a few comments over the years, from the "Who will look after you when you're old?" (as if all no child ever pre-deceased their parents or became estranged or moved across the world), "You'll regret it" (even if that were the case, surely it is better to regret the lack of a child than to regret one you have?), and my personal favourite: "You won't know love until you have a child" which makes me feel sorry for the people who say that. Not only did they clearly live a life devoid of love before parenthood but they're enough of an arse to judge others on the basis of their experiences and feel entitled to share that opinion.
Don't want a kid? Don't have one. I think children are something you need to really want to do because it looks like bloody hard work. Anyone who tells you you should have kids because it's just what you do/they wish they hadn't and how dare you enjoy your life/they want grandkids/it's selfish not to is an eejit of the highest order and should be ignored.
(p.s. to the poster who asked why non-parents post on MN - aside from all the non-parent forums (I googled something and ended up in the feminist forums), have you considered that it's a good place to see the other side of the coin? I have family and friends with kids and reading stuff here from the perspectives of parents is useful.)