I agree with you. Some of them are sincere. To some degree, Catholic Church also has ideal about social justice that is many Democrats share, as well as anti death-penalty. They're, however, also against things that most Democrats embrace, such as abortion, gay marriage, freedom from religion, and so on. These things really turn them off (and Christians in general) that at the end they prefer Republican.
Ooopss... social justice that many Democrats share...