You're out of power, you're being treated horribly, you're angry, and you can't reach your real enemies. So you attack the allies that are in easy reach.
It is cowardly. It makes it easy for your enemies to divide and destroy you.
The conservatives are right. We are undisciplined. Faced with a challenge, we turn to fighting among ourselves.
This election looks like it is the Democrats and the progressives to lose, and we may lose it because we can't direct our anger at our real enemies.