The most recent lecture I heard was Kamal El Mekki's Holiday Season - An Islamic perspective. In this hour long lecture, Kamal El Mekki goes over in detail all aspects of why we should not celebrate holidays other than the 2 Eids. One of the interesting points he made was that when Islam had the upper hand, meaning when it was in the height of its success and power, non Muslims wanted to emulate us. For example when Muslims first came into Spain, the young Spanish men started to dress like Muslims and act like Muslims even though they were Christian. The same can be said for today when Islam does not have the upper hand. Young Muslims have taken to imitating and emulating the Western norms in the world. The biggest export from the west to Muslim countries is popular culture. Music, films, fashions. This all leads us to see why Muslims of today celebrate things like Thanksgiving, Valentines day, Mothers day etc.
Later on in the lecture this hadith was brought up:
Anas (may Allaah be pleased with him) said: "The Prophet sallahu allahi wa salam came to Madeenah and the people of Madeenah had, in Jaahileeyah two days for play and amusment10. So the Prophet (SAW) said: 'I came to you and you had, in Jaahileeyah two days for play and amusement. Indeed Allaah has replaced them for you by that which is better than them: The dav of Nahr (Slaughteung) and the day of Fitr (Breaking fast).'
I think that this is the best hadith to really show that no other holidays or celebrations are necessary. It shows that it does not matter if it is a secular holiday or not. As Muslims we don't celebrate anything but the 2 Eids. It makes it quite simple. There is no arguing about origins of celebrations or holidays because all of that does not matter.
Every day we recite Al Fatihah in our salat at least 17 times. In the last few ayats we ask Allah to guide us to the straight path. The path of those who have earned your grace. Not of those who have earned his anger, or gone astray. When we celebrate the holidays of non Muslims, we are going astray. Allah knows best.