It seems terribly important to Jesus that his disciples not "cause these little ones to sin." Better to die that do that. But who are these little ones, and how can a disciple cause them to sin?
I think they are people young in age or faith or both and thus susceptible to learn corruption from sinful elders. Martin Luther King Jr. said that one of the worst things about racism is the corrosion of the soul it inflicts on the victim. Physical abuse, false teaching, breaking the marital vows - the list of woes is depressingly long but God's alternative is simple: learn the truth, live the truth, and speak the truth in love. From the inside out and all the time. Little ones can sniff religious phonies a mile away, but love and integrity draw them like pantry flies.
The heartbreaking thing is that little ones can't always protect themselves from corrupted big people. Jesus is telling big people that they wll answer to even Bigger People. So unless they want two angels named Vito and Guido measuring them for cement overshoes, His disciples had better not "cause these little ones to sin." Jesus has a dog in this hunt, as they say. He is days away from suffering torture and death to provide eternal life for "these little ones." The last thing he wants is for any so-called followers to call his sacrifice into disrepute. No wonder he tells us, "so watch yourselves."
And yet because I too am a "little one" in his eyes, forgiveness is for me, too, if only I will come to Him and say from the heart, "I repent." Until that awful moment when the sea I am about to be thrown into is made of fire, it is never too late. But the sooner, the better.