I think the problem with Kollel today is that it puts a stress on society at large, which puts pressure on others who want to support Kollel to do illegal things to keep up donations. No, its not everyone, but it happens. I wonder if taking money for learning that causes enough stress on the donor to steal is better than the kollel man learning part time and working part time.
But I do agree, if someone voluntarily gives money to support Kollel and the man is learning properly, that is his job.