No, that is a mere assertion (which may or may not be true). If they claimed that he is wrong because he is engaging in motivated reasoning, then that would be ad hominem.
Wait, what? This might be a little off topic, but if you assert that they lack evidence and are drawing conclusions based on motivated reasoning, that seems highly relevant and not ad hominem. I guess it could be unnecessary, as you might try to focus exactly on their evidence, but it would seem reasonable to look at the evidence they present, and say “this is consistent with motivated reasoning, for example you describe many things that would happen by chance but nothing similar contradictory, so there seems to be some confirmation bias” etc.
If someone else accuses you of engaging in motivated reasoning that’s ad hominem.
No, that is a mere assertion (which may or may not be true). If they claimed that he is wrong because he is engaging in motivated reasoning, then that would be ad hominem.
Wait, what? This might be a little off topic, but if you assert that they lack evidence and are drawing conclusions based on motivated reasoning, that seems highly relevant and not ad hominem. I guess it could be unnecessary, as you might try to focus exactly on their evidence, but it would seem reasonable to look at the evidence they present, and say “this is consistent with motivated reasoning, for example you describe many things that would happen by chance but nothing similar contradictory, so there seems to be some confirmation bias” etc.