Is it permissible to visit a colleague in a private place belonging to his deviant sect to offer condolences on the death of his grandfather?

It is recommended to offer condolences to a Muslim in their affliction, for the Prophet, peace and blessings be upon him, said: "Whoever consoles an afflicted person will receive a reward like theirs," and he also said: "There is no Muslim who consoles his brother in his misfortune but that Allah Almighty will clothe him with garments of honor on the Day of Resurrection." Condolences are valid in any place, and the fact that a person is an innovator (mubtadi') does not prevent one from offering them condolences, as jurists have permitted offering condolences to a disbeliever, so a Muslim innovator is even more deserving. Condolences fall under the category of good treatment, and one must be careful that they are free from any forbidden aspects or from condoning the mourner's falsehood. A Muslim should only associate with the good, and not frequent gatherings where much idle talk and gossip occur.