In my experience, the ones claiming to represent police and fire benevolence associations are the worst in that regard. Many of them have administrative costs of nearly 80%. Yet they try to make it sound like they are like the usual police and fire charities, the kind that locally hold the "fill the boot" drives with off-duty firefighters collecting for local charities and such. No thanks.
Some of you may know I'm a police officer. My police association does not solicit money over the phone for two reasons:
1) We think its despicable to solicit money from hard working people when they have no idea that only 10%-25% of the donation is going to the charity.
2) We don't need your money and dont expect you to give your money to help us advance our causes.
There are, however, some good police related charities, for example, the (insert city here) police widows fund, but if you feel like you want to help them out, please call them and pledge your money directly to them. No middle man needed.