This implies that the concerns are all about the composition of the breast milk. What if they did find that milk from trans women is safe? Would you be fine with it then? Considering how many people are mentioning fetishes and paraphilias, I think that's what people actually care about and the milk composition thing is just a way of making the petition sound reasonable. Which, actually, you're implying in your second paragraph. In fact you're very strongly implying that in your second paragraph and I didn't notice it when I first read it.
Tbh I think if everyone's main concern was the safety of the drugs used to induce lactation there would be a bit of intellectual curiosity about that in the discourse. It comes across more like an attempt at a logical justification for a disgust reaction.
I don't agree that questioning the safety of the baby drinking the "milk" (if it even is the same as female breastmilk) and questioning if the baby is being used as a prop for a sexual fetish are mutually exclusive.
There are lots of issues that are raised here, and I don't feel that the physical safety of the child should be a minor one.
I think part of the misdirection that gender identity ideologues are relying on is that the focus of the current debate is around whether or not biological men can actually breastfeed (as evidenced in my post above about Suella Braverman's dismissal of the issue yesterday as nonsense because men can't breastfeed).
Gender identity ideologues are relying on the confusion and debate around whether it's even possible, because then the argument doesn't move onto the next logical question, which is "ok, so if biological men can make something that looks like milk come out of their nipples, what is its chemical composition, is it like female breastmilk and is it actually safe and beneficial for babies to be drinking whatever it is that's coming out of there?". Babies are very limited in what they can drink safely (and with adequate nutritional value) for the early months of their lives, so this is a potentially life-threatening issue.
Obviously, there is the fetish issue to address as well, and clearly that's not merely a minor issue either, but as we've seen, it's quite hard to prove that someone else is acting out a fetish when the cultural narrative is framing that as another example of prejudice, akin to people associating homosexuality with paedophilia.
Yes, obviously the fetish angle should still be highlighted, but I think the most urgent issue here is "should that tiny baby be drinking whatever it is that's coming out of that man's body?".