People act like babies are sensitive, super special glass statues that need all this special treatment to turn out good and will break in a million pieces if everything does not perfectly suit them, yet when it's time to raise them they back away and go all "but they're only three/four/five/six!". Fucking pussies. No wonder people end up the way they do.
Feed your kid as you wish, as long as you don't fire breastmilk down its throat with a shotgun.
Funny, because isn't your avatar a hipster Hitler? Ignore them. It's not like you decreed to never touch your baby ever. If you don't want to have to be bitten by babies, it's no one else's business. My solution? Eat the ones guilt-tripping you. They sound like fools.
My nephew was day-one formula-fed after my sister-in-law tried breastfeeding him once, he wouldnt latch and gave up completely. Didn't even look at using the breast pump.
However, in her defense, formula these days is pretty darn good in terms of nutrients, and Zach didn't suffer for it, he loves his mum no less.
Kudos to you for wanting to give your bub breast milk, it's your choice and yours alone how you feed your child. Let people like that stress themselves about it, it's still not going to affect what you do for you and your baby.