Yeah, so what’s going on here is that they’re laundering a reactionary class position through rhetoric. They’re chuds roleplaying as Vulcans.

Never believe that [transphobes] are completely unaware of the absurdity of their replies. They know that their remarks are frivolous, open to challenge. But they are amusing themselves, for it is their adversary who is obliged to use words responsibly, since he believes in words. The [transphobes] have the right to play. They even like to play with discourse for, by giving ridiculous reasons, they discredit the seriousness of their interlocutors. They delight in acting in bad faith, since they seek not to persuade by sound argument but to intimidate and disconcert. If you press them too closely, they will abruptly fall silent, loftily indicating by some phrase that the time for argument is past.

Actually, I’ve seen transphobia be called structurally anti-Semitic and I have to agree. The reactionary logic behind the wave of anti-trans hate is essentially the same as previous waves of anti-Semitic hate throughout history.

Minors are typically considered to be under 18. But sometimes they are also considered under 21. But now there is a popular psychology meme where you are actually a minor until your brain magically develops at 25. So “minor” is being extended to be as late as possible to delay transition as much as possible.

The age of puberty is on a secular decline, at first due to higher nutrition, but now possibly because of industrial pollutants. In 1991, female puberty in Danes began on average at around age 11. In 2006, this dropped to just before age 10. The ideology of cissexism puts endogenous development of the body on a higher metaphysical level than exogenous puberty. It is “naturalized” even though it’s obviously historically contingent. Cissexists take it for granted that the individual would not want their physical development altered exogenously. Thus, it is perfectly acceptable for a 10 year old to undergo puberty if it’s endogenous, but as soon as it’s exogenous, the individual no longer has the “emotional” or “cognitive” maturity until they are 16, or 18, or 21, or 25.

There is a conflation of puberty blockers and HRT. Puberty blockers were developed to prevent precocious puberty, but can obviously be used in other circumstances, such as to give a young individual time to determine which puberty they’d like. Because of societal cissexism, an unofficial compromise position was struck where trans children would be put in arrested sexual development until they are 16 or 18 to appease conservatives (I am not sure when or how this became the de facto line on healthcare for trans youth, but its prominence is reflected by you immediately assuming only blockers are being discussed here). Actually, HRT has, can, and should be given to people younger than that, but to do so legally almost always requires the consent of the state and the parents, with the well-being of the person actually affected completely marginalized.

“Irreversible consequences” is quite the rhetorical trick these reactionaries like to use. Typically, it’s used against transmasculine people as a means to draft them back into the reproductive role they were supposed to grow into according to patriarchal logics. I believe there’s overlap with the sexual politics of conservatives towards teens and the fact that the US successfully combating teen pregnancy is a significant cause for the drop in American fertility rates. There is also some white supremacy at play here of course. As for puberty blockers, the reason they were upheld as a compromise is exactly because they do not have significant irreversible consequences on bodily development. Except, long-term use does create issues such as osteoporosis. And there is also the matter of being forced to be pre-pubertal while all of your cis peers get to develop. But that is not a concern to reactionaries. If puberty blockers are said to lead to irreversible damage by them, it is because they want to brand them in the same way they have done to HRT in an effort to ban them and force trans people to undergo extremely damaging puberties.

Do they think they’re doing bottom surgery on toddlers?

They don’t think they’re doing that, but they do say it, yes. Actually, bottom surgery is done non-consensually on intersex babies all the time to reify sex! Bottom surgery for trans people does the opposite of reify sex, which is why their position is “hypocritical.” As in, it’s actually not hypocritical if you look into the logic of their beliefs rather than try to make sense of the words coming out of their mouths.