big difference between voluntarily giving to the poor vs and having someone decide and tax you for it.
Yeah, the first is very often paternalistic and patronising, tends to be highly selective and carry all sorts of hidden, and not-so-hidden, agendas, while the latter is about acknowledging the existence of society and the arbitrariness of wealth-distribution.
I'm not a huge fan of charity - have encountered quite a few people who were involved in it for dubious reasons with very questionable motivations. Jimmy Saville would be a very extreme example, and hence a bit unfair, but I've met people who appeared to be doing it because, for example, they liked getting to boss poor people about, and to feel superior to them. Some work for charities to facilitate social-climbing and networking or just to get a huge salary.
Many charities have an obvious religious proselytising agenda, others are just lobbying organisations for the rich (all those 'think tanks'), and at best they can be a last resort where the state has failed in it's job (often due to the effects of those lobbying organisations).
Also a few charities here seem to fall into colluding with the government's agendas, like disability and mental-illness charities getting too involved with Tory 'welfare reform' programs.
The most difficult cases would be trans-national ones. As there's no global state, in those cases it is often charity or nothing, so it's kind of a necessary evil. And both private foreign aid and state aid have a long history of being misused (e.g. the recent Oxfam sex-abuse cases) but on the other hand there's no other mechanism for helping those in poorer countries who suffer disasters. In those foreign cases private charity and state aid aren't that different, both can have the same pitfalls.
Within a country though, I think if there is a lot of charity, then there's something wrong with the society.