Infertility as a result of puberty blockers (and hormones, but it is incredibly uncommon to prescribe them to kids in the US or the UK) is actually fully-reversible. The only long-term effect is a (very slightly) lower bone density, if you're on them for ten years. [Note on this at the end of comment for pedantic people]

Pretty much nowhere is it standard practice to administer hormones to anyone below 18, and few people are advocating for that.

The rate of attempted suicide in people yet to transition with gender dysphoria is 41%. That is the highest rate of any physical or mental condition we have on the books. This rate drops when you put them on hormone blockers (in cases of minors) and it drops when you put them on cross-sex hormones (in cases of adults).

Getting HN to come around on this issue is likely impossible, but if you want to hear from an actual expert (effectively the expert on the topic), here's a presentation you might find interesting from a medical doctor:

https://www.youtube.com/watch?v=fefu33e8O-0

If not for compassion, you should check it out for intellectual curiosity. The talk goes into a lot of detail on how a general human's endocrine system works, has some interesting medical information even if you're not trans, and takes a really balanced approach to the issue.

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[Note] Fertility returning by simply stopping anti-androgens isn't necessarily a given, but getting it back is actually entirely doable. If you take the time to watch the talk, the doctor goes into how he's managed to get 100% of patients desiring it fertility back.