A good friend posed the hard issue: Could she be friends with a Christian who holds the belief that mixed-race marriages are wrong? She says no, and dumped that friendship on that basis alone.
Since something like 75% of America considers themselves Christians, that would make things challenging. If I went down my list of ideologies I thought were intolerable, I would be stuck lonely, wishing I could even avoid myself (with whom I disagree most often). If sinlessness is the arbiter, then I dare not pick my friends this way.
For me, I expect Christians to struggle with sin. We go into this whole thing pretty much in tune with the fact that we sin. We get it, Catholics, Protestant both get this. Naturally, people disagree with what counts as sin. Racism is a bad thing, there is no doubt, but it is just one on a long list of egregious grievances. Which sin is worse in the eyes of God?
Grading sins is easy. We like some more than others. Some are fashionably accepted as tolerable (or even nudge-nudge OK), while others are despicable unacceptable.
Pick your favorite? Drunkenness? Prostitution? Divorce? Stealing? Lying? Racism? Abortion? You get the idea. The list can go a long way before exhaustion.
Jesus Christ Himself famously loved the worst of sinners. He ate at their homes.
I considered my friends. I know many, many people who have strong views I consider contrary to God's plan. Some are Christians. Some are activists. All are sinners. Just like me.
Got a sin that you put higher in the hierarchy?