The problem is the so called Christians who ran (like Cruz) are not really Christians in their behavior. They make us look bad too. I would love to see a real Christian run and run a Christian campaign instead of trading on the name of Christ like Cruz, but I have not seen one yet.
This is a huge problem with the type of individuals you are talking about. This scripture verse captures their attitudes in a nutshell:
Proverbs 30:12
12 There are those who are pure in their own eyes yet are not cleansed of their filthiness.