I know several people that have claimed that. But, I don't know how you prove/disprove it.
I doubt Jim Robinson would willingly give identity information to the IRS. And he certainly wouldn't do so without notifying the target -- unless the IRS were to somehow suborn the DoJ into using a NSL (National Security Letter) to give up the info, while keeping the inquiry confidential.
Otherwise, if you aren't posting info that can be used to identify you, the IRS doesn't really have a way to find you.
I think it's more likely to be targeted after a conservative organization is forced to give up a donor list. I suspect THAT has happened, and perhaps there is an overlap. But, that was during the Obama regime.
I have talked with Freepers who claim they were targeted after being at Freeps every year thereafter that Clinton was in office.
See Post 114. Just FYI.