You know maybe they were looking to provoke violence. I have a difficult time getting inside the head of a racist to try and figure out their goals. They are by definition, irrational thinkers, which makes it very likely that their motivations, actions and goals are disconnected in any event.
To iterate rightleft's response in a slightly different direction:
They're perfectly rational. They're just starting from a position that you hold to either be irrational, entirely emotional(and likely reflexive and thus unthinking in nature--so quite literally irrational), or of such a nature that even contemplating that particular starting point is so mentally revolting that your mind just simply rebels at the idea(and thus conclude it is irrational).
It's moments like this where I have to wonder if I'm in the club of people that if placed under a FMRI scanner, I'd turn up with a brain scan that would closely match some of the worst criminals(and politicians/Business execs) in history, as I don't seem to have that particular reflexive mental gag reflex. As disturbing as those lines of thinking are, on personal ethical and moral grounds(never mind external ones), venturing in that territory is almost on par with discussing the weather and its impacts in some respects.
For "leadership" within most Supremacy groups, or really any agenda based organization that seems to be centered around the premise of amassing and accruing influence and power. They're going to determine how to "sell" their particular agenda.
If you're willing to discard personal ethics in pursuit of your goal, the most effective means of gaining and keeping influence quickly(aside from sex) is by means of emotional appeal, as it triggers instinctive responses in people who are then going to be inclined towards making irrational decisions because they let their emotions decide for them.
The next best option for the unethical playbook is appeal to the person's "sense of ego" while also stroking an emotional chord at the same time. This is something that both even the "moderate left"(never mind antiFa, who does it too) and the "Alt-Right" do.
"It's not your fault your life hasn't gone to plan. If only it wasn't for ____ your life would be much better. Join me/us in pursuit of _____ and soon enough all of your problems will be solved because we'll make sure nobody will be able to do ____ again in the future." Because hey, if they're offering to share (some form of) power with you personally, it can't be all bad, right? There ain't no interest like self-interest after all.