Hm, I suggested a simple thing and now this becomes another discussion filled with hate and accusations.
Nobody could really know how the visitor numbers would change after the cap was introduced - to me my arena seemed pretty logical but now I think I would do a little bit better if I got rid of a few k bleachers and replace them with more expensive seats.
I think if you have to pay the same amount for reducing seats as for building them you get "punished" enough - but I really dont think people in Boston intended to "punish" players for any mistake they made in the game... If you can build sthg. you should be able to demolish it if you want imo.