When dogmatic belief dies all that is left is subjectivism, and when subjective belief (which is never more than mere opinion) dies all that is left is sentimentalism.
Our society now is awash in sentimentalism. Most every argument is now a sentimental (or utilitarian) argument. Here is an example: Slaughterhouses kill animals so we can eat them. Vegetarians feel bad about this. Not only do they want to not eat meat themselves, but they don't want us to eat meat either.
Most of them have no philosophical or logical reasons for banning meat. They might have moral arguments--that factory farming and slaughterhouse practice is un necessarily cruel and barbaric--but mostly their argument is sentimental. Killing animals makes them feel bad.
Sentimentality lead to violence when sentimentality becomes an ideology. An ideology is a single driving idea that sweeps every other consideration aside. Those who follow an ideology are always self righteous, and they will use every means possible to enforce their ideology. The ideologue may attempt to argue logically or philosophically, but this will only be a tactic--it is not because he believes that logic, philosophy or theology have any real weight. These disciplines will serve the ideology--the ideology itself may never be questioned. Not only logic and philosophy are subject to the ideology, but all things are subject to the ideology. All other considerations are subject to his ideology--including moral considerations.
So the sentimental ideologue will eventually force his opponent to conform. He will use any means possible--political legislation, financial pressure, social pressure, shouting more loudly, imprisonment and persecution and finally bloodshed if necessary.
This is why the Catholic faith is the sworn enemy of every ideology: because the Catholic faith insists that there is a higher truth, that there is an objective truth and that it is revealed by God--not made up by human beings. Every ideology--whether it is economic or political or sentimental or erotic or ecological or social--every ideology will find the Catholic Church to be an obstacle.
The ultimate irony is that every ideology (like every heresy) is partially true, and it would find it's fulfillment within the fully expounded Catholic faith.
The way, therefore to counter the ideologies is not for Catholics to be better ideologues, but for Catholics to be better Catholics.
Update: The Anchoress writes here some further thoughts on Sentimentalism. She contributed a chapter on this awful "ism" for the book Disorientation.