"It wasn't a big thing" - how do you know? You do not. A group of people ask for a place at the table and you and your ilk question their legitimacy as human beings - that's what you're doing. People are saying "I feel this way, I am this way, I see others who feel like me and and feel empowered to come forward and live as the person I feel I am"
And your response is 'it's a phase' - like their identity is a fidget spinner. Nothing is being lost or endangered by making trans people feel welcome and valid and allowing them to pursue treatments that make them happier.
The topic is not taboo. What's taboo is invalidating the lives and existence of other human beings just finding a voice and a place in the world and figuring it out. After all if it's a phase, or a social contagion, it'll blow by and you can relax - but the amount of effort going in to making these people feel scrutinized and unwelcome doesn't seem like that's the point at all.