I put down a Magma Totem to try and interrupt, and someone on my team said in /say "Would you cut it out!" We lost.
You can interfere, thus dragging the process out and coming off as a sped to everyone, or just let these folks get their achievement and then leave or go back to fighting to win - your choice.
Smart thing to do is not interfere (or just do something other then BGs that week) because the harder you work to prevent people from getting their meta achievement, the more times they're going to have to queue up and make your life miserable thanks to Blizz's idiotic decision to force non-PvPers into the BGs.
I know the official excuse is that by forcing peeps that normally wouldn't do BGs to do them thanks to the meta that this will result in new players getting into PvP but let's be realistic, this is a miserable XP for most of them thanks to a combination of lack of gear making them gank bait and folks like the OP doing their best to interfere.