why do we hold that the fish cooked in a pot used for basar beforehand is mutar to eat with even if it was hot, seeing as the radish is asur because it tastes sharp, shouldn't hot food be stricter than cold food with a sharp taste, considering that even the heat created during shchita is enough to pasul other hot meat (because the knife used in shchita is now asur for use with other hot meat)?
zach masi, montague MA
See Tosfos DH Hilchesa. There are two basic ways to reconcile this question. The first Lashon of Rashi is that if the fish was cooked in a meat pot it is Asur, and the Gemara is discussing a case where a hot fish was put on a cold plate or vice versa. The second Lashon is that if it cooked in a pot it is Mutar but the case of the radish is worse because the knife has oily meat fat on it and there is actual Basar (and not just Ta'am).