everyone of those has long lost it's pagan origin, and are merely a commercial parody of what they really were... whoever these days belonged too have long been disowned. (btw. Valentine is based upon Saint Valentine do some better research!)
and easter is the feast of pass over, but is given the wrong translation in English due to the KJV... in Europe it's spoken as it is... in dutch we celebrate Pass over and call it PASEN. (again, better research please!). And easter eggs that go with it, is again nothing more then a commercial parody about the feast of easter... noone even knows what a chocolate egg supposed to mean or ment on easter... let alone worship them.
noone knows who Mitrash is, or what he did... we don't even know from a historical record for crying out loud! but again, are you saying this in trying to defend that Islam is full of incorporate pagan rituals? cause then you are allready admitting that Islam has paganism in it.
The Muslim by using this argument is actually admitting that the Qur'an was not "sent down" but fabricated from pagan sources. This means he has become an unbeliever (Surah 25:4-6). And it is a false analogy to parallel the pagan origins of the rites commanded in the Qur'an with the present day holidays nowhere commanded in the Bible. What some modern day Christians do on Dec. 25th has no logical bearing on what the Qur'an commands Muslims to do (eg. the Pilgrimage, the Fast, etc.) It is irrelevant that some Christians choose to celebrate the birth of Christ. Since the Bible nowhere commands it, it is a matter of personal freedom. But Muslims are commanded in the Qur'an to believe and practice many things which came from the paganism of that day.