I recommend reading FIUV Position Paper: Liturgical Pluralism.

It is refreshing to see that I am not alone in seeing nothing wrong with having a multiplicity of rites and uses in one Church, whether or not in communion with Rome. The more narrow-minded clergy and faithful believe that tolerance in this matter encourages disunity. Perhaps, to the contrary, the more the liturgy is “policed” and uniformity enforced, the more man’s rebellious spirit will enter the fray.

Pope Benedict XVI himself has noticed that some of the faithful have been alienated from the Church by the new liturgy. He could say that those people should be forced, and that the more Catholicism would be ugly, nasty and make them suffer, the more they would become meritorious and holy. There are a few fiends commenting on blogs with exactly this attitude. But, the Holy Father has said many times that he believes in liturgical diversity and peace in the Church.

Liturgical pluralism is a source of vitality and strength, of tolerance and unity in charity. I recommend this article with its wealth of references in the footnotes.