I don't think the protests will lead to anything, except venting, and I would not have any interest in attending one myself.
And of course, like any protest involving millions, there are going to be ratbags. But I also know people who attended the protests, here and the US, and they would have behaved completely peacefully.
Even if you don't like what is being protested, the right to protest is part of any free society, and should be defended (and of course anyone protesting should also be responsible to do so in a non violent way).