@motherapple If this is the only context he’s being aggressive with the baby, and you are able to manage getting enough exercise and mental stimulation for them, I don’t think re-homing is the only solution. If they were being aggressive in other ways, then maybe that’s something to think about, but in this context, he’s kinda doing the best he can for someone he recognises as a dependent part of the family, and there are a lot of benefits to that kind of behaviour (like when the kid is older and starts playing in the yard/street, etc, you pretty much got a full time nanny who will always keep tabs on them), but I get that you have to consider if you have the energy and patience to work through a period of successfully curbing the extremities of that behaviour while the baby is so vulnerable.
In saying that, I don’t have any personal experience with this kind of situation from the perspective of a parent, so take it all with a grain of salt, but I did grow up as the kid of a family in this kind of situation. I don’t think our heeler was around when I was a baby, but I have very early memories of how protective he was of me, and how gentle he was with me. If anyone but my parents (even them sometimes too lol) tried to pick me up, he absolutely was not having it. An annoying inconvenience when you’re trying to carry a sleeping toddler in from the car, but big peace of mind when I’m off playing in the yard, on a busy street with a lot of people walking by, some definitely not the kind of folk you want within any proximity of your children, but woe to anyone who might try anything with that dog around.
The main catalyst that made it work in our situation was that he was so gentle with me. He would nip my ankles when someone was holding me and wouldn’t put me down (no blood or bruising, but the same scary enough thing with your baby), but when I was interacting with him, god, he couldn’t have been more loving and patient. I used to climb on his back and pretend he was a motorcycle, like hold his ears like they were the handlebars, like in that classic questionably rough way kids can be with pets, and he didn’t bat an eye.
My point is just to consider all the details of your situation. If our dog was ever directly aggressive towards me, my parents definitely would’ve rehomed him. Even if it was in that way, where they can’t really help it because their rescues who have some ptsd issues (thinking about a heeler we had later in life who was so sweet, just the best in so many ways, but would only give you one warning if you ever tried to touch her butt before just ripping your hand off. In this context, my dad probably would’ve been too nervous about if I touched the dogs butt accidentally, etc, but then also some dogs, like the one I grew up with, have extended patience for the ones they know are more delicate and dependent, so yeah, have to consider the dogs personality)
Lol I guess what I’m saying is, make a graph with protective and helpful benefits on one axis, and negative aspects on the other, and then see where your specific situation lands. Good luck! I hope you can get to a solution where everyone is safe and happy.