On reading the OP, two questions immediately sprung to mind:
1) How do you know he has thousands of accounts?
2) How do you know he boots all the male players and only plays against female players?
But as the others have already said, if you have proof then send it in.
And as BlackBogey says, take what your wall-poster says with a pinch of salt. There have been many players with multiple accounts (the Cheezynutz clan from around 2010/11 comes to mind, and a couple of years ago I saw many accounts of the same name barring a numeric suffix which were all obviously the same person), but WGT don't seem to care so long as money is being spent. Reminds me also of a player, again back in 2011/12, whom I reported to WGT and they disabled his account. He then posted on my profile wall with 5 other accounts saying something along the lines of "maybe you want to report this account too", and "or this one", and other similar messages. Although these multi-accounters may not be spending money, they will be making others part with theirs. Multiple accounts also makes it look like WGT membership is high, making it look good for shareholders and prospective players, but most of us know the reality is different.