Diversion to another question, to a side issue, or by irrelevant objection
Example
"I think that we should make the academic requirements stricter for students. I recommend that you support this, because we are in a budget crisis and we do not want our salaries affected."
Topic A is the proposal that academic requirements be raised. Topic B is the possible effects of a budget crisis on teachers salaries. Topic A is abandoned and the unrelated topic B is introduced.
Form
Treatment
Dealt with by refusing to be diverted from the original question, but stating again the real question at issue