I just went through Capital's "last 10 songs" list on their website, and it's true, they haven't played 1D at all today.
Also, I'm pretty sure I just went to the BRITs website and voted there. There was no condition of me ever having to have listened to Capital before, or be a fan of the station. So despite it being apparently being voted for by Capital listeners, I reckon a high percentage of those votes weren't even by Capital listeners.
Dropping them from the station because of their on-stage error does seem a bit childish, but if Capital never really wanted to play them in the first place, then what they did isn't exactly going to make them want to play them, so fair play in my eyes.