Can i disable the STEAM_ID_PENDING kicker?

No. Short version is BAT needs the steamid to validate into something. Longer version is that BAT does not consider a player fully conneted untill he has a proper steam id, and him never doing this will create problems. There is also the side issue with that fact that when players STEAM ID dont validate their most likely on a hacked/cracked steam account or perhaps the server your trying to host is cracked (Its offcourse posible with a bug in either BAT or steam somewhere).