It depends.
Calm, normal and rational people who protest like civil and decent adults = no.
Middle class lefties who've suddenly decided that they don't like democracy because it didn't give them the result they liked = Yes. Every time, yes.
And how do you distinguish between the two?
There's a good portion of that crowd who are anarchists and idiots, yes, but there's going to be people there genuinely scared out there.
Instead of laughing at them, it'd be nice if the PM came out and tried to understand them for the first time in his life. There's a lot of frightened people out there because they've been told £12bn of cuts are coming but not had the courtesy of being told how, when and where.