I find that when you point out the simplicity and uniqueness of salvation by faith alone, people see it as a license to sin. Therefore they reject it because they think grace makes us hypocrites. They fail to realize that we are hypocrites by nature. Grace then becomes an offense in their minds.
They also fail to realize that the flesh always sins, so... it's *impossible* to stop sinning. The opposite could be argued that salvation isn't a license to force yourself to stop
sinning, or hallucinate and self-deceive yourself to the point you think you're indefinitely sinless. Oh but you need to have an outward profession and show OTHERS your human works so they can physically "see" that you're a Christian... because clearly salvation from God
requires that other people
(who have nothing to do with God) visually see your works. Oh, but if they're blind then I guess you're screwed.
But yeah I guess soon as grace as mentioned, the natural hypocrite in everyone has to jump out and start going on about how you must stop sinning--because how could anything truly be "free"?