When I was a teenager a Christian Camp leader gave a talk on why girls should dress modestly. His logic was that by dressing immodestly girls were inciting lust and causing men to sin. he didn’t actually say that causing someone else to sin is itself a sin. How could he. The sin is in the human heart. The Bible clearly teaches that until people sinned they cared not a wit about nudity. He implied it though. He implied that it was somehow unkind of girls to make it difficult for those poor old men to keep their thoughts under control.
Like most ideas whether you agree with them or not there is some truth. Is it a sin to stir up the sinfulness that is at the heart of us all and if so how much? Quite a number of things have been historically considered sins because they may tempt the weak to fall. Drinking alcohol is clearest example but dancing and gambling have also been on that list. Most people are tempted to hate by harsh words but kind words can bring out hatred also. Not many people will continue to like you if you tell them they are wrong no matter how kindly you do it.
My opinion and it is only my opinion is that it is not a sin to ‘make’ other people sin. No one makes you sin. It is spiritual immaturity to think so. Children blame others for their behavior but they are children after all and not 100 percent in control of themselves. Adults take responsibility for their behavior. An immodestly dressed person does not make anyone lust anymore than a harshly speaking person makes you hate. Lust and hatred in those situations are natural reactions of the flesh but we have the choice to control the flesh.
On the other hand is there a Christian teacher anywhere who would advocate harsh language and personal immodesty. You might get a few somewhere to say it is okay under certain circumstances but not as a life style.
Speaking of Christian teachers, I have heard teaching against murder, adultery and stealing and I have heard sermons teaching against the lead-up sins of hatred, lust and coveting. I have heard some teaching against causing people to lust but not much against causing people to hate or causing people to covet. I am a great believer in symmetry. If a Christian should endeavor to help his neighbor to not lust by dressing modestly then a Christian should also help his neighbor to not hate by speaking modestly and to not covet by living modestly. Not because I am my neighbor’s keeper but because I love my neighbor.