What annoys me are all the charity collectors (known as "chuggers") who constantly knock on my door. They try to get you to sign up to make regular donations by bank transfer to whatever cause it is.
I don't like being repeatedly disturbed at home, especially as whenever anyone unexpected knocks it's almost never anything good (some of my neighbors are dodgy people). And you know these people are earning money on commission for every one they get to sign up (I believe they are employed by profit-making private companies who in turn are contracted by the charities).
Plus, having dealt with charities a couple of times as a supplicant (and also having done voluntary work for some), I don't really like most of them (with a few exceptions) and I don't much like the sort of people who work (as paid employees) in the charity sector.
Many of them are in that line of work for entirely self-serving reasons. Either to further their career, in a very cynical way, just to get some lines on their CV because they can't get a proper job in whatever sector they are interested in, or to earn as much money and perks as they can (especially the case for those at the top of the charity sector, who often earn a fortune) or just because they enjoy bossing the supplicants around and acting like Lord or Lady Bountiful. In some cases they are outright abusive (cf the scandals around some of Oxfam's overseas operations).
Charity is not the noble, righteous, thing it's made out to be. It's riven with dodgy motivations and questionable practices. And that's not even considering the fact that elite private schools and right-wing lobby groups that propagandise for the interests of the rich (like the Institute of Economic Affairs or umpteen others) are classed as 'charities' in our stupid system.