The other issue is that there is no good way to link to a specific flag from an accusation thread saying "if you want to support this accusation, go here". You can link to the inactive flag list or to the trust page, but the actual flag could be there or not, depending on viewing person's trust list. And if the scammer has multiple flags then extra steps will be needed to verify which one is the one you want to support.
I don't think the intention is for people to be leaving knee-jerk reaction support/opposition to flags. If you are going to support/oppose a flag, you should read it, check the thread that it is referencing, and check to make sure the OP listed in the flag matches the OP of the thread in question.