Let puberty run its course then decide.Considering a Trans person is born Trans, the only thing the hormones do is make the dysphoria worse because the body is changing in opposite to what the Trans person's gender really is.
Blockers stop that change from happening too soon, to give the child a chance to figure things out.
Really I'd think people would be for the blockers; it keeps "people who aren't Trans" from being so and figuring out if it truly is "just a phase", or perhaps figuring out their gender fluid or something else.