As a colleague I might think it's kinda funny or at least weird, but I wouldn't ridicule him over it. As an employer.. I dunno. It's not so much the look but the fact that someone who wants to wear that all day (especially at work!?) might be a bit flaky in some way. I guess also it's the look, because it might cause a lot of unwanted workplace drama. And if customers can see him then it might give them a bad impression of the company. I don't necessarily think it should give a bad impression, but you have to be practical.

I wouldn't really care but my work is full of shit talkers so he would probably not have a good time

I already work with a ton of babies.. But I don't think that's appropriate work attire, might send the wrong message ("we're anti-child labor laws and how do ya like that!").

Nobody is more anti-pants than I, If he did his job and wasn't a pain in the ass to work with I wouldn't care TBH, as an employer I would let anybody who could work from home anyway so whatever...if he had to be in the office I would have to insist he wear something over it, even babies wear clothing