That's a common enough platitude in the Church these days, but Bishop Brown of Orange, California, seems to take it a little more seriously than most, because on his account just about every single person in this country is in a state of mortal sin every time they recite the Creed at Mass.
Whhhaaaahhh? you might reasonably wonder. Well, Bishop Brown supported Fr. Tran in his determination that those who refuse to continue standing after the Agnus Dei, in clear violation of the liturgical norms of USCCB Region XI, are in a state of mortal sin simply by virtue of their refusal to conform to the liturgical norm. Since just about every Catholic I know of fails to bow his or her head at the appropriate moment in the Creed (at the words "by the power of the Holy Spirit...") at Mass, in clear violation of the liturgical norms, which require said bowing of the head...well, you get the picture, cartoonish as it is. (See the Curt Jester for a summary of the merriment.)
When I was first received into the Church in 1983 the pastor of the parish in which I was received was one of these liturgical Nazis who insisted on forcing everyone to do things his way even when his way was very different from some very old traditions that have substantial and powerful rationales. Some of these old traditions, abandoned by the banal liturgical planners of the 1970s, have since been re-introduced into the GIRM, and rightfully so.
Liturgy, of course, is not necessarily about the continuance of every and all traditional practices--it is first and foremost about the unity of doctrine as expressed in the unity of practice, and certainly things would be much better if we all did them the same way. What one bridles at here is not the mere fact that kneeling has been abolished, but that it has been abolished in such an uncharitable manner, apparently without any regard for local practices or the feelings and sentiments of the faithful. If the feelings and sentiments of the faithful happen to be heretical, then it's not so clear that one must make allowances for them; but when the feelings and sentiments of the faithful are perfectly in keeping with what the Church herself has sometimes required, then it may be appropriate to make allowances, if only under certain conditions.
Next thing you know they'll be making it virtually impossible to hear a Latin Mass...oh, uh...hmmm...never mind.