By not trying to root them out now they will inexorably take over whatever will be left of ukraine. That's almost always what happens with radical armed elements, and as I said they are getting way more comfortable with not even hiding anymore. I can't think of any example where fighting side by side with radical extremists didn't end up backfiring. And beyond that I mean if the UA government can't even get their soldiers to not wear black sun pins openly and openly & explicitly promotes azov on social media, that really does not sound like they are even reluctant to have them on their side.
It's a war and I totally get that it's dirty and that you can't pick and chose your allies everytime. But nazis are an easy line to draw.