The Achronim have an obsession — among others — with discovering “Lifnei Iver” everywhere.
I don’t remember the names, but a whole slew of Achronim seriously discuss the possibility one who chooses to die rather than transgress a sin that isn’t on the list of the Big Three commits “Lifnei Iver” toward the non-Jew who kills him (in violation of the latter’s always-ignored “Sheva Mitzvos Bnei Noach”).
I just saw in Rabbi Nissim Karelitz’s “Chut Shani” one who allows himself to be nudged into selling an item that wasn’t for sale again commits “Lifnei Iver” toward the man violating “Lo Sachmod”. No source needed, either, as though the comparison to Ribbis is obvious.
As the saying goes: הזהרו בבני עניים שמהן תצא תורה (Nedarim 81a). Why do the poor become Torah scholars? Because they lack money to buy Achronim…
Update: Shut “Betzel Hachochma” part 3 siman 50 also denies “Lifnei Iver” applies when bowing to “Lo Sachmod”, and quotes the Minchas Chinuch who agrees. The Merceves Hamishneh Hilchos Gezeilah 1:9 reportedly disagrees, however. See the last page of this book.