I'm not sure I understand, you're angry with the vendors essentially for not taking a side, your side, in the march?

There were far more of them, yes, but also far more of you than your solitary aggressor. I try to put myself in the situation as you describe it & I don't see any basis for these vendors to become involved. Based on what you write you had the situation well in hand. They're there to sell their products, not police demonstrations, or become involved in ME politics. If you'd been physically attacked, outnumbered or threatened with violence, that would be one thing. But you evidently weren't.

Don't go back. But don't kid yourself, based on your own account you're not punishing them for apathy, but for not visibly taking your side in a highly charged issue.