It you feel you need help with a simple set of injections and a grumpy baby for a couple of days then parenting will be a tough ride.
You have no idea how you would have coped being the sole carer of a baby from newborn 24/7 with no emotional support from a partner.
Your DH works full time and works away sometimes. We get that. He is also presumably not an arsehole, supportive of you and a present father who is willing to share, and capable of sharing, equal parental responsibilities when you are both in the same place at the same time.
Bit different to OP, no? Again - you have no idea how you would have coped doing it solo from day one. Hopefully people wouldn't have suggested you aren't a capable mother for struggling because I don't know many people who say such flippantly nasty things.
Anyone with any sense has responded to the OP's predicament as a whole, not for inexplicably fixated on the injections.
If she had a partner pulling his weight and she had to go to the injections herself obviously she would have been fine.
She was using it as an example of something she has had to do on top of everything else on her own while being on her knees and sleep deprived.
Maybe you didn't understand that. Or maybe you're just in a bad mood today. I hope you can find a way to be happier in yourself so you don't have to write posts dripping in judgement to feel better 
With women like you, who needs misogynists.