I would support a sort of method that sits in somewhere in the middle.One thing I find annoying is the fact that my empire is viewed as abhorrent if we go to war to demand that somebody remove a colony they established near our space that is frustratingly close to my borders. You're the one who set up that colony, tentacles for eyes, on the 9 tile arid world in orbit around the 25 tile alpine world that I needed! Is it so wrong that I force you to evacuate your colonists before you're properly established?
Why does cleansing work in the perspective of murdering colonists, anyhow? I guess it makes sense for a fully populated planet but if it's just a starting colony without a planetary administration? I think there should be a consequence-free war goal to force an opponent to abandon said colony without it being considered purging. It should be viewed more as an evacuation, honestly.
A wargoal that allows you to evacuate the pops at some cost (it shouldn't be free, you can't relocate your own pops for free), but it only works while they have somewhere to evacuate to, either their old empire, if that empire accepts them, or empires that have a policy of accepting refugees. If there's nowhere for them to escape to, you're given the option to either purge them or keep them, and you eat the penalty if you decide to purge them.
And it's still regarded as a minor atrocity. Forcibly relocating people is still a pretty major crime, just not as bad as an outright genocide. Like how the Trail of Tears is seen as a horrible crime the American government committed against the indigenous tribes, but nothing nearly as bad as, say, the Holocaust.