I definitely know what you mean, Andrew. There are a lot of Christians who think that it's wrong to be friends with those who aren't Christians... or even to get involved with them in any way. The truth is, when Jesus was on earth, He accepted and talked to sinners. All kinds of sinners.
"When the teachers of the law who were Pharisees saw him eating with the 'sinners' and tax collectors, they asked His disciples: 'Why does He eat with tax collectors and "sinners"?' On hearing this, Jesus said to them, 'It is not the healthy who need a doctor, but the sick. I have not come to call the righteous, but sinners.'"
-Mark 2:16,17