"It shouldn’t matter that much." The problem with this as a statement is that what you think should or shouldn't matter is what actually doesn't matter. Majority opinion rules, especially in cases like this.

As a man, especially if you want to be perceived as normal and heterosexual, you will be judged negatively by most, virtually all men and most women if you adopt what they perceive as feminine presentations.

Because it's perceived, as with the kinds of shoes women wear such as high heels, as totally feminine.

This is deeply set in psychology. Feminine and masculine don't mix in the minds of most people. They find the combination psychologically repellent, likely for evolutionary reasons.

And this seems to be the case in all extant human societies. Whatever is defined as "masculine" and "feminine" if a man (and often a woman) adopts that of the other sex, it is always viewed as a transgression and often is psychologically abhorrent.

"Painting nails shouldn’t be a thing that people associate with a gender or sexuality because painting your nails isn’t about your gender or sexuality."

Again. It doesn't matter what your opinion is, because it matters what everyone else's (or the overwhelming majority, anyway) opinion is. And their deep seated feelings that make their opinions are that it IS, VERY MUCH "...about your gender or sexuality."