I agree with Wolf that Naaseh Odom was not put there for no purpose other than to trick people. It was put there to teach the lesson of anivus (humility).
Similarly, all the issurim in the Torah were put there for a reason, not to be machsil. Kol mah shebara HKBH b’olamo, lo bara davar echad levatalah. For example, the shratzim are a crucial part of the food chain, although we may not eat them. The tayvah of arayos is necessary for kiyum haolam. We don’t find anything which is totally useless other than as a stumbling block. And if takeh the RBSH did put in a stumbling block, then after meah vesrim, one could claim he was an onus. (I.e., if a miracle happened that every statue of yoshka suddenly came to life, do you think the RBSH would hold it against the masses if they thought he was telling them to convert to christianity? Ein lo ldayan ella mah sh’enav ro’os.)