Ad hominems are formal fallacies. They are not valid deductive reasoning.

But people basically never use valid deductive reasoning for anything. Using available evidence to make predictions about things and act on those predictions is fine. If somebody has a history of poor thought or writing and then I encounter more of their thoughts or writing it is not unreasonable to say "this new material is likely to be poor and I don't need to spend time on it."

If somebody says "hey do you want to see Transformers 7", responding "I did not like Transformers 1-6 so I'll pass" is fine even if it is not deductive proof that you won't like Transformers 7.