Neither hot, nor cold

On one side were the saints, those who followed the Sermon on the Mount. On the other side were the criminals?

No!

We all know that the majority were not following the Sermon on the Mount. Consider the US, a Christian country.

But Paul chose one particular blacksmith/worker as a villain, because he opposed their message thoroughly. (Wait, wasn't everyone opposing it?)

No, he was an interesting villain. Paul saw something in him, and it was a part of his plan to evangelise the Gentiles.

Both saints and sinners are interesting, only the lukewarm Jesus spits from his mouth.