Yes, I do board, but our BO is adamant about horses being respectful and people being safe, so he has said many times that if you need to smack another horse with a lead rope to keep yourself safe and to keep the horse respectful, do it. That being said, I have seen the turnout guys (who are boarders themselves) smack obnoxious horses with a lead rope to get them to move or to leave a "weaker" horse alone. The only "rule" is that you don't hit them in the face or near the face. When I flipped the lead rope at Willie and Bo, I made sure to aim for their chest or flank (whichever presented itself to me).
Most of the geldings in turnout are respectful and will walk away once you've chosen a horse to halter. My friend's arab gelding, who is best friends with Aires, was being a little pushy and clingy with me but all I had to do was point and say "CJ, go away" and he wandered off and didn't bother us. Of course, most of the other geldings are worked with every day or are older and know the rules. Willie is young (I think he's maybe 4) and I have seen his owner at the barn once in the two and a half months I've boarded there. She doesn't ride him, nor does anyone else. He stands in his stall unless he's turned out. So, I'm kind of not surprised he has bad/pushy ground manners (he's even pushy in-hand).
If this type of situation arises again, I will carry that lunge whip with me when I go to get Aires.