The fact that something is 'artificial' (i.e. a product of art, essentially) does not mean it is 'arbitrary' (i.e. just a product of freedom or authority -arbitrium-). Do not take social norms as 'arbitrary': they usually have deeper meanings than what we usually assume.

I am not saying you are obviously wrong. I complain about the 'arbitrary'.

In Western cultures, educated criticism is always enveloped in smoothness, and language is an important part of this envelope. This is not evolutionary, it is cultural and we do it because, in the long term, society has noticed that this is useful.

Academia is the classical example of this: one may hate his colleague in the same Department, and also his ideas, but one is not going to bully him linguistically in a paper. Because the time spent in explaining the insults is not worth it.

Unless one is a simple bully, obviously. But this is not the usual state of affairs.