Because practicing Catholics who vote democrat are blue collar union democrats or JFK-type democrats.
The democrat party AND the republican party have shifted left. The Obama administration has displayed strong favoritism towards being "green" - at the expense of union jobs (XL pipeline is an example). And JFK would fit right in the Republican party today.
Catholic attitudes haven't changed...the two major parties have.
That can't be it.
They don't like the changes we've made because now they're stupid!
Currently, the white Dem party seem primarily government employees and dependents, and radical feminists.