No one is forcing anyone to upload an image of themselves, so let’s stop telling that story. 
It is not unethical to encourage someone to upload an avatar to a discussion platform; this is a common way people tell users apart at a glance while using forums.
Forcing users to upload images of themselves (not sure how that would ever work) is not the same as encouraging users to use avatars in forums. 
If you think so, please start a new topic laying out your argument. It is noted that for this discussion you are against the practice as a whole, which is a valid perspective, but does not lend much to a discussion concerning “best practice”. 