I not agree.
It's just annoying when you have a team and someone is trying to steel all youre good drivers on youre own server.
I kick people too if they do that ! Sorry
I don't know how to translate your comment... Well, there are two ways.
1st. Steel your team's good drivers
2nd. Steel any good drivers not in your team
Well if any of your teammates leave from your team to go to the one who is recruiting, they should't be in your team at first place = no need to be in your team.
On the other hand, if he/she "steels" any or all of the good players in your server, but not in your team then why weren't in your team ? As a conclusion, good or not, if they wanted to be in your team they would have been by that time.
So, as you see, both explanations are wrong based on common logic, and banning should or must be avoided. Ladder servers have to be public, and ban should be applied to cheaters/hackers or to any who behaves in an extreme way.
In your case i would try to warn first, either by asking to stop or by muting for some minutes and unmuting after, in order to check if behaviour changed.
Personally, i wouldn't do anything of the above, cause i know which members i have and how strongly bonded are with the team = no fear about recruiting by others. Also, don't forget that everyone is free to join in any team he/she wants.