Free Republic is a for-profit corporation solely funded by taxable donations from its members. You may not deduct contributions to Free Republic, so the IRS would not be auditing you for that.
I have heard that people who have been audited are rich fodder for the feds to audit again. That could be the cause of your close scrutiny by them.
If they audit you and find you’re short on your taxes, you will get audited again until they owe you or you’re even.