It really makes no sense when muslims try to justify the celebrating of these holidays. If one has a muslim family, why even celebrate or commorate these holidays? Why even entertain the thought of it? I see absolutely no reason to. The fact that one would want to when they have a Muslim family (not reverts or not alone in their Islam) reveals their weakness of being a follower and the state of their iman. If they were in another country that for example did not celebrate thanksgiving would they celebrate it?
Their argument is that thanksgiving is merely a "custom" (aada) with no religious connotation which is far from reality. In Shariah things are looked upon in terms of reality and not how we want it to appear as. Thanksgiving for example is specific to non-Muslims, so it would fall under the hadith of the prophet (sallahu allayhi wa salam) "The one who imitates a people is from them." Ibn Tayimiyah mentions that imitating them, the kuffa is necessitated by following those things that are specific to them and their culture/history/religion, he says, "Muslims resembling them in their celebrations leads to them (the kuffar) being happy with their falsehood that they are upon"
Ibn Qatum states that congratualting them in their holidays (specific to them) is HARAM by consensus of the ulama. What more proof do you need other than logical Islamic sense? I don't know maybe ISLAM?!