The reason people can't understand the comment about sterilisation is because there has been a general degradation in people's ability to understand comments contextually. This is everywhere, in politics, in discussions about television shows, etc.
It's like there exists in a whole section of the population an inability to think beyond one sentence to the sentences that surround it, much less to comprehend anything like words that have more than one meaning, or hyperbole, or sarcasm.
Her explanation of her comment was pretty clear, and made sense in the context of the larger conversation. She things there are some choices people make where ethically, they should also then refrain from having kids. Those choices are not very compatible with putting the needs of kids first.
That's not a hugely controversial position - I imagine lots of people could think of situations where they would feel that followed. Is it the case with the decision to transition - well, it's not a crazy idea, in the sense that motherhood and fatherhood are deeply sexed roles, and that affects kids. - it's a pretty valid question how that affects kids.
Compared to the very controversial opinions that people are rightly allowed to debate in public spaces and on social media, that one doesn't seem on the farther side of crazy.