It's OK to completely change your physical appearance and way of life for the person you love, even if he makes no sacrifices at all (from The Little Mermaid). This movie has the single most appalling ending of any Disney movie ever made, which is a shame because, apart from that, it's a great film. I just cannot comprehend how anyone could make a movie in the late 1980s with this message, which is not exactly subtle: Ariel gives up her home, her family, and BEING A MERMAID because she loves Eric so. And he gives up … nothing. Yeah, that marriage is off to a great start.
At least he included the movie as a good movie. In fact, this was arguably the most important hand-animated movie of the last fifty years. After years of shoddy animated movies, Disney probed that it could still make one as good as any produced under Walt. It was the first of two decades of great Disney movies.
Regardless, it has been attacked since it came out. Feminists didn't like it because Ariel chased a prince and was eventually rescued by him. It didn't matter that she saved his life twice and he saved her twice. They didn't give the movie much credit for presenting the first Disney prince with a real personality or the first time that Disney had an actual courtship between one of their princesses and her prince.
But, that's not Geekdad's complaint. His complaint was that Ariel became human in order to be with Eric. Is this a valid complaint?
Keep in mind that staying a mermaid was a deal-breaker with their romance. They could only have a tenuous relationship on the boarder between land and sea - an environment that was dangerous to both. The choice was transform or give up someone you love.
This is not the same as having breast enhancements. The closest equivalent is leaving your native country to marry someone.
I'm sympathetic to this. My daughter moved to England to get married. A close friend moved to America from Canada to marry his girlfriend. I used to work with a German woman who married an American serviceman and moved here. She had to give up her language.
By Geekdad's reasoning, all of these choices were appalling.
Also, it was established early in the movie that Ariel was fascinated with the surface. You got the feeling that she may not have been ready to make a deal with the devil but she would gladly have traded her tail for legs, even before she met Eric.