Ok here's my perspective - we don't really know why he's against it so I'd refrain from making assumptions about his maturity. See, I personally have no problem with what people do to their bodies - implants, tattoos, piercings, lipo, etc. Their body, their choice. I even have a tattoo myself. But here's the thing for me, I'm simply not attracted to certain body mods. So does that make me a douche? I dated a sweet girl with implants, but it just didn't work out in the bedroom which led to a mutual breakup. So are my sexual preferences "shallow"? You'd agree girls who date guys based on preferences in height, which they have the complete liberty to do so, are also "immature"?

Even if this wasn't the case for him, I wouldn't call him out just yet because most of the time these problems are more nuanced than we perceive.