That speech in Alliances was way too on the nose, but I don't think the problem is the content.
The whole concept of Star Trek is that they don't put their survival before their principles. Allying with the Kazon would have meant enabling them to murder and enslave people. In The Void when one of their allies kept on acting like a pirate they were kicked out of the alliance. So sure, alliances would be great, but an alliance with the Kazon isn't worth the moral consequences.