Why is this question primarily opinion based?

Question

I recently answered the question, Why are hens so different from other birds? When I came back to the question just a few minutes ago, I noticed it had been closed as 'primarily opinion-based'. Now, I know this isn't a particularly high quality question. It doesn't show any research effort and it's perhaps too basic for this site¹. If the question had been closed as too broad, or unclear, I would understand, but I don't see what about it is opinion-based? I'd like to know for my own edification.

^{1: And perhaps I shouldn't have answered it; I'm not a biologist, and I have no special training in biology, I'm just someone that likes to read about biology. But I like this site, and I feel this kind of basic question may be one of the few places where I can contribute to it.}

Related: Question that can be answered using commonly-available references on-topic here?

Answer 1

For me, too broad or unclear would have been the preferred reason for closing this particular question. However, I suspect that it was the second sentence that triggered the primarily opinion-based close:

Compared to other domestic animals it seems to me they are the least capable of defending themselves or escape if it comes to be left alone in open wild.

This is clearly just an empty statement, not backed up by any evidence, and most attempt of such a ranking would probably devolve into personal opinion.