I believe if everyone who was against the current oligarchy started placing guillotine stickers everywhere, like you might for a favorite band, people would feel less isolated in their distaste for the current system.
And in an ideal world those who the guillotines are for might realize just how much they are in the minority.
Not sure. There are a lot of symbols used in the past that have come to mean one party or another. That’s likely to happen again with any “common man” symbolism.
For now, during times of fighting against the oppression, a guillotine works to symbolize the movement.