It is an error to think that reductio only applies to “physics and math problems”. Logic is logic, it applies to all truths. (Though one has to be careful with things stated informally, to ensure that one is working with the claims that were intended. There is a danger of parsing an informal statement as if it were a formal statement, and as a result interpreting it to mean something other than what was meant.

Also, there may be a risk of people being more likely to derive in invalid ways when attempting the reductio, like making some hyperbolic statements, exaggerating the implications of a statement, and treating those exaggerations as if they actually logically follow. But this doesn’t make reductio an invalid technique, just one that people can fail to use properly.)

Like I said in the other comment, the objection should be that the derivation of the absurd from the premise is invalid. For example, pointing to the “that you can stomach” part of your claim, and saying that the derivation was invalid in neglecting that part of the statement.