It helps separate principled people from others. Some will say "countries must never be invaded, occupied, or annexed", others will add "... if it's done by Israel, but I'll absolutely ignore/support it if it's done by Turkey, Russia, China".

And the latter group is fundamentally not principled, they are biased to the core, and this is an easy way to tell them apart.

It's like people who are against capital punishment vs people who are against capital punishment when it affects them & their friends.