Self-confidence always goes a long way. You might also find some solace in the fact that there’s been a big culture shift since G4 first aired in 2010 and now. Millennials and zoomers have gotten older and are a lot less judgmental when it comes to enjoying kids media, often because they themselves enjoy some childish stuff as well.
Look at how Lego has continued to grow in popularity with all age groups for an example. Or the general growth in popularity of animated shows and movies. Or how Pokémon is (I think) the single biggest IP on the planet. Just some examples.
Just try to be confident and comfortable with yourself, and know that the vast majority of people simply don’t care. And those that do, well, they usually don’t matter. If not MLP they’d likely find some other issue to nag you about. There’s no keeping someone so concerned with other people happy.