Right I don't think J. Smith would be considered a pedophile based on medical diagnosis standards and as far as the law goes he probably would be convicted of bigamy.
Quite possibly.
I believe though, we can make judgements on the ethics of his behavior. Even in his day his behavior was considered morally wrong. He violated the marriage contract with his wife. She did not accept polygamous marriages. His marriages were in no sense similar to legal contractual civil marriages in which typically the man is responsible for the woman's well being both physically and emotionally. The only purpose and benefit he appeared to get from the (polygamous) agreements was sex. He used his authoritative powers to manipulate and take advantage of others for self interest. The "Fanny affair" was an indication of his moral behavior even in his day. It was an affair. It was unacceptable by those close to him then.
While I think Joseph Smith sexually, emotionally, and spiritually abused some of his followers, I think it's also important not to assume he did not have a way of justifying his behavior, or that there wasn't some degree of sincere belief in his rationalizations. I think there can be a knee jerk reaction to Joseph Smith's practice that assumes lust as the sole motivation, similar to what Americans thought about Mormon polygamy in Utah. This fails to consider the long history of Christian polygamy and concubinage that extends back to the Reformation. Can one reasonably think that the founder of a radically extreme and fundamentalistic restoration movement would not broach the subject of plural marriage at some point? i don't think one can understand Joseph Smith's practice without considering the possibility that he may have had theological motivations as well dating back to the dictation of the Book of Mormon. While I think plural marriage was on Joseph Smith's mind since 1829, his ideas about how to go about it probably evolved. It is likely that when he was confronted by others about his behavior--such as in the Fanny affair--that he gave theological justifications, which resulted in Cowdery and others adding to the 1835 D&C an explicit statement that monogamy was the rule of the church.
In his 1842 letter to Nancy Rigdon, he did not deny the pleasure aspect of plural marriage, but he also outlined the means by which such behavior could be justified--revelation and commandment. He also fully acknowledged that apostate Christian America would not understand the principle. So, there are complex issues involved, and I think the lust argument is too reductionistic.
When I argued that Joseph Smith should be judged by the standards to his own time, it was in regard to the issue of pedophile and marriageable age. In other words, it was about something for which he and others would not have the same sensibilities as we do today. So I was advising not to commit the fallacy of presentism. In the case of plural marriage, he and others involved were fully aware and intentionally violating the law as well as cultural norms in order to live what they thought was God's law. In such case, it is difficult to label such behavior as unethical, unless one assumes--as you do--that Joseph Smith only wanted sex and didn't believe his own rationalizations.
What he was like even in those days is comparable to men in positions of celebrity status today. If you take a male movie star adored by young females fans in their teens, I'm sure many who chose to use their status do bed many women, and many much younger than themselves. I'm not saying that all male celebrities would behave that way, but for some if the opportunity is there they will take advantage of it.
Why do you think it's OK to force Joseph Smith into this model? Would you not think it strange if someone tried to apply a theological model onto the rock star's behavior?
Smith had the interest and the opportunity. He could manipulate people for his own ends and he did. It would be considered unethical then as well as now, for anyone in a committed legal relationship to break it.
First, you are assuming insincerity to prove insincerity. Second, you are assuming the law decides what is ethical. Monogamy might be a cultural norm, but in and of itself is not more ethical than polygamy. If Joseph Smith and others chose to live polygamy, they might be violating the law, but they were not necessarily less ethical than monogamists.