This is a malicious little strawman you've cooked up here. It was made clear that he's highly untrained, we know NOTHING about his personality, and it's been stated many times already in this thread that warding/banishing sorcery works on the exact same principles as summoning/binding sorcery. So no, sending this dude back with half-filled-in knowledge and no training is NOT going to increase our chances of Dia being okay. It's going to blow up in our goddamn faces in approximately 99% of all hypothetical outcomes.
Trying to suggest that we don't love our mother because we're not going along with your ridiculous and uninformed plan is just petty and transparent.
Making arguments is fine, but base them on the merits of the plan, don't try to bully people into them.