I agree it’s poor form to poach players from active coalitions. It shouldn’t be done. And it goes beyond bad taste and into the bizarre if the primary goal truly is, as has been suggested, to actually sabotage those coalitions.
I also agree that advertising active coalitions to non-coalition-engaged players in inactive coalitions is solidly healthy for those players and for the game, given that the in-game coalition tools are lacking.
The group of coalitions I’m a part of (TP9) finds both of the above points to be obvious and uncontroversial as a matter of policy. I obviously can’t speak for other groups.
But if anyone feels like your active coalition is a poaching target, why not start by talking directly with the person responsible and their group? Then, whether you foiled their nefarious plot to bring down your coalition, or they approached you in error, you’ll actually know the facts according to Mystery Poacher X, and we can all respond accordingly.