i don't think either case has been stated as bannable. I don't know if either is bannable. The first one certainly not lol. I don't see how it could be.... If they didn't want you summoning him at an enemy crystal.. they could code it that way... since you cant summon them at the crystal in the castle anyway. So they can program him to not be summonable there, they could make it so you cant summon him at an enemy tower. They didn't, so my logic would be LOL, i think he was just mad.
Using towers to bring them to the gate, i don't think is bannable either. Cause i have used Flame towers to take down a gate (not putting them in a line) and it lured the NPCs over... Wasn't my intention, but still happened. This one though i don't think is bannable, more of a low-down cheap thing to do.