Okay, but they're a significant fraction of the total number of signs.

"By any means necessary" was the co-equal largest sign I spotted in a video of Columbia protests. If you're carrying a "Release all Palestinian political prisonsers" sign, and you look over and see a dozen people carrying a giant "By any means necessary" sign, wouldn't the appropriate thing to do be to tell the "small number" to roll up their giant banner that, if believed, might well justify the Israeli response?

If you're gathering under a huge "Victory for Palestine" sign with your "Ceasefire Now!" sign, wouldn't you maybe...camp somewhere else?

I don't doubt that the fraction of agitators and violence-promoters may well be very small, but the voice is loud and the large number of other protestors are complicit in endorsing the message.

If there's some tiny "from the river to the sea" sign somewhere, it's different than if the most prominent messages are the hard-line ones.