Heard it was a good show and can't really judge people for liking a cartoon; if I ruled the world, the 90s X-men cartoon and Batman animated series would both still be airing thanks to everyone involved being held hostage. There's a difference between liking something and using it to identify yourself with, however, and I reserve the right to feel the same way about self-confessed "bronies" as normal people would feel about me if I walked around in public wearing plastic Wolverine claws and yellow spandex.
Also, anyone who wears a fedora in public and isn't named Indiana Jones should be executed on the spot as a general rule. For the betterment of mankind.
I watch Batman TAS and other cartoons from my childhood and from others' childhoods. Still, I think there's a lot of ways in which an adult can enjoy something like this, and I don't mean just ironically, but some of them you can't deny will grant you the manchild insult label (and that may be the least insulting option) with no possible defence from your part.
I have watched kiddie stuff either in the company of other adults or shared my thoughts on those afterwards. I don't even have to use nostalgia as a shield, as some of them aren't from my childhood. I bring up the animation, the writing, the character designs, the voice acting (which back then used to be fantastic in my country), the direction, the reasons of its success or demise... as an adult fan of animation in general I like to learn about the production values.
Say I like the first Digimon. I sat to rewatch it with adult glasses because of nostalgia. I was aware since childhood that it was an anime to promote all kinds of consummerism: Digimon sold everything... and yet, I never felt the need (as a child or adult) to buy any of its products, I thought the anime was itself a decent and complete product and it stayed that way. I was aware of most of these following things, but the important part is that they remained strong against scrutiny: the collectible monsters here were charcaters in themselves, not mere tools, and complemented well with the children protagonists; children all had their idiosyncrasies, one of them being adopted (and at the time, it was refreshing that the adults writing the cartoon didn't deem it a thing to be ashamed of), two of them's marents were divorced, etc.; the story took place mostly in a fantasy world much like wonderland (but "digital"... it was an excuse) but then at some point they returned to Tokyo for a period, it was refreshing being exposed to the modern japan through it at that age, but this device also made it feel very grand and exotic... compared to a fantasy world!
Well, those are my reasons to like digimon (first series) as an adult. But what if instead of just appreciating it when I'm watching and discussing it, I just couldn't move on to other things, what if at my age I daydreamed, no, wished about having digimon exist, be my friends and take me to the digimon world? That's a trillion steps from "redefining adult".
I didn't dislike bronies when I thought it were people that saw episodes of it and thought to themselves (and could argument!!!): "hey, that wasn't so bad. It's got a better moral than those other boys' cartoons about solving everything with violence", that they were people that were conscious of how the collectible character genre (and industry) worked and so they wanted to take part in it with their custom made figures (kinda creative, not awfully creative), etc. But when I dig into say, brony community endorsed documentaries, that's not the image I get.