The statement by the "scholar" is a parody; and yet, the quotations are actually grounded in legitimate Islamist thought.
Shirk is worse than Killing
Since Jihad involves killing and shedding the blood of men, Allah indicated that these men are committing disbelief in Allah, associating with Him (in the worship) and hindering from His path, and this is a much greater evil and more disastrous than killing. Abu Malik commented about what Allah said:
﴿وَالْفِتْنَةُ أَشَدُّ مِنَ الْقَتْلِ﴾
(And Al-Fitnah is worse than killing.) Meaning what you (disbelievers) are committing is much worse than killing.'' Abu Al-`Aliyah, Mujahid, Sa`id bin Jubayr, `Ikrimah, Al-Hasan, Qatadah, Ad-Dahhak and Ar-Rabi` bin Anas said that what Allah said:
﴿وَالْفِتْنَةُ أَشَدُّ مِنَ الْقَتْلِ﴾
(And Al-Fitnah is worse than killing.) "Shirk (polytheism) is worse than killing.''
Islamic scholar: "Saying Merry Christmas is worse then fornication or killing someone"
Yes, as this Muslim "scholar" (unidentified) claims, saying 'Merry Christmas' is shirk (polytheism) and kufr, and he cites Ibn Qayyim as saying that shirk is worse than killing. He is probably referring here to Ibn Qayyim al-Jawziyyah, a famous student of Ibn Taymiyyah. Ibn Kathir, who was also a student of Ibn Taymiyyah, noted in his tafsir of Q 2:191, drawing upon hadiths, that "al-fitnah is worse than killing" means 'Shirk is worse than killing'
http://www.qtafsir.com/index.php?option=com_content&task=view&id=233
Likewise, for verse 2:217, Ibn Kathir notes
"[...](...and Al-Fitnah is worse than killing.) means, trying to force the Muslims to revert from their religion and re-embrace Kufr after they had believed, is worse with Allah than killing.' Allah said:
(And they will never cease fighting you until they turn you back from your religion (Islamic Monotheism) if they can.)[...]"
http://www.qtafsir.com/index.php?option=com_content&task=view&id=196
Of course, it is not necessary to turn to hadiths to extract this interpretation, because the Quran itself repeatedly mentions disbelief--and polytheism is one of the main forms of disbelief--as the worst crime (6:21, 6:144, 6:157, 7:37, 10:17, 11:18-19, 18:15, 18:57, 29:68, 32:22, 39:32, 61:7).
Anything that tempts a Muslim toward polytheism, such as participating in other religions rituals, especially those specifically involving what Muslims and the Quran consider to be shirk and kufr, such as claiming Allah has a son, is fitnah that leads Muslims toward disbelief and therefore to destruction in hell-fire. In classical Islam, a Muslim man who sincerely utters "Merry Christmas," knowing what this means, has committed an act of apostasy, and he would have to repent, or else be punished with death.
Non-Muslim dhimmis are already condemned because of these sorts of transgressions, so they are subjugated under Islamic law.