I've been dumped off the 91 bus, too, because of a manifestation. I wasn't in a hurry, so it wasn't a big deal, but if I'd had to get to a station to get a train it could have been a big PITA.

No bus in Paris is a good idea if you have to be somewhere at a certain time, or if you are in a hurry.

Perhaps the Roissy bus is an exception.