FWIW I don't automatically think of crazy extremists when I see that flag just based on the design, but going around America with a 1% Muslim population is going to lead to misunderstandings.
Hopefully, someone just assumed it was a religious flag.
They are. The above poster is just an idiot.
The Taliban's flag is the tawheed flag (better known for its unmodified usage by ISIS), except with black lettering on a white background. That is the flag the demonstrators are walking under.