I've no issue with angel investing. It does start to irk me when people talk about it as 'giving back to the community' though. That used to be called charity, not investment.
However, giving back to a professional community seems like it would run on a different set of fundamentals to giving back to a social community.
Could one not equally apply the argument to non-monetary activities -- giving talks, running events, writing OSS software, etc? That's all stuff that normally falls under the mantle of giving back to the community, yet it often confers resume benefits.
If you've got the spare time, cool, if you've got the spare money, cool. What's the issue here?