Right. It's not about the Catholics or Protestants at all; this is a division within Orthodoxy. And to compare our rejection of the innovative calendar with the rejection of traditional Christian holidays by extreme Protestants is ludicrous: we are fighting to preserve tradition, they are fighting to destroy it!
What I have said below I have said in other forms earlier, but for the sake of sprtslvr and other inquirers I am repeating myself so they don't have to read through a zillion posts to find out what exactly the Old Calendarist objections are. I am also providing links to documents that explain our position in greater depth and breadth.
It's only about the Catholics and Protestants to the extent we Old Calendarists believe the calendar change to be motivated by ecumenism, i.e. the teaching that Catholics and Protestants are still somehow part of the Church, the Body of Christ, despite the fact that Catholics and Protestants have different doctrines and practices from us. The teaching that the heterodox are still part of the Church entails that our doctrinal differences are not significant, meaning that our Orthodox teachings and practices that differ from the West are not necessary for salvation and are up for discussion. The ecumenist teaching, or heresy as we traditionalists view it, is most clearly seen in the teaching that heterodox Baptism is 'valid' (see end of this post).
Note that I am not making a clear distinction between doctrine and practice. The reason is that there is no clear distinction in Orthodoxy: we profess our faith not only in word, but in deed. The festal calendar reflects our unity of mind as Orthodox; calendar divisions reflect our loss of unity. When we celebrate the Great Feasts together with the Western heterodox, and not with our Orthodox brothers who celebrate on the traditional calendar, we express our unity of mind with the heterodox, while we express our lack of unity with our fellow Orthodox (not to mention the saints and angels in heaven). This is an important point, because a typical argument from some new calendarists goes as follows: 'well, even conceding that the calendar innovation brought disunity to the Church, the innovation has no dogmatic significance'. Yet any kind of disunity very much has dogmatic significance, because it violates our belief in 'one holy, catholic and apostolic Church'. This is the position of the Greek Old Calendar Church as shown in our confession of faith of 1935.
The idea behind the ecumenist push for the calendar change is that by changing our festal calendar to conform to that of the Western Christians, we will help to heal the divisions. In other words, since our divisions are not in fact significant for salvation, as we are still part of the Body of Christ together, we should reflect that by unifying our practices. Traditionalists like myself, on the other hand, believe that the Orthodox Church is the Body of Christ all by itself, and we don't need to make any concessions, and in fact any concessions would be a betrayal of the faith.
The Dogmatic Significance of the Festal Calendarhttp://www.roacusa.org/Catechism/THE_CALENDAR_QUESTION.pdf
Fr Basil Sakkas explains the problem from the traditionalist perspective better than I ever could. The clinching evidence that the calendar change was motivated by ecumenism is seen on pp. 11ff., where Fr Basil proves this from the text of the Ecumenical Patriarch's encyclical of 1920 "To the Churches of Christ Everywhere". He also explains the dogmatic significance of the traditional calendar in general.
Note on ecumenist ecclesiology:
For anyone who wants proof that recognition of heterodox baptism is now the official teaching of the 'mainstream', i.e. 'World', Orthodox churches, here is a statement from SCOBA in 1999:http://www.scoba.us/resources/orthodox-catholic/baptism-sacramentaleconomy.html
A critique of the errors of this document by the conservative New Calendarist Met Hierotheos Vlachos is seen here:http://orthodoxinfo.com/ecumenism/methierotheos_baptism.aspx
For anyone who wants to offer up the earlier practice of the Russian Church in receiving Catholics and Protestants without baptism as evidence that the Church has always recognized Western baptism, here is an explanation of that practice by Met Anthony Khrapovitsky:http://www.roacusa.org/MetAnthonyEconomiaintheReceptionofConverts.PDF
Met Anthony explains that the practice must be understood as an exercise of economy, not as a recognition of the validity of Western baptism.