First of all, it isn’t mass flagging. You’re also partaking in help with derailment towards the thread. People have every right to flag a post if they feel it is in violation of the Forum Code of Conduct.
Just because a post of yours get flagged by the community, doesn’t mean they don’t have the right to do so. In the end, it is for the moderation to decide if the post does violate the Forum Code of Conduct, and what actions to take, not the community.
Now, just like everyone else, I’d suggest also in not derailing the thread, and hijacking it.