Polemic writing usually focuses on controversial topics in which the writer tries to persuade the reader to take an unpopular or unlikely point of view. To say that charities are bad certainly falls into that category.
Here are a couple of supporting points you might consider using:
1. Charities are bad because they give people a false sense of altruistic activism. In other words, they make the donor feel like they are doing something significant when really they are not. In some cases, people feel like the other bad things they do are canceled out because the donated a few dollars to a charitable cause.
2. Much of the money given to charitable causes never makes it the needy. It is eaten up in “overhead” and “administrative” costs.
3. Some people who might otherwise be productive members of society become dependent on charity. Then their children do too.
As far as your headline is concerned, it should be a little shocking—the reader should be surprised by it. That will make them want to read further.