Interesting point, but surely the reasoning that they are "only facsimiles of the connection found in a deep and long relationship" is a major argument for regarding them as morally wrong?
If you believe you have a moral duty to be the best person you can then passing up that opportunity in favour of the facsimiles is morally wrong.
> If you believe you have a moral duty to be the best person you can then passing up that opportunity in favour of the facsimiles is morally wrong
Maybe a better statement would be that casual connections only offer facsimiles of the depth of a deep and long relationship, because the sheer accumulation of time and experiences with another person cannot be replaced quickly. However, you can also say that a deep and long relationship only offers a facsimile of the breadth of many shorter relationships, as one person can only offer so many things. If you change your passionate pursuit every decade, finding a partner with the same one each time might make that pursuit more fruitful. It's not how I personally feel, but "best person" is subjective like that.
I don't think this follows unless you think there is something particularly special about sexual relations per se. I'm monogamous but I don't see why people should avoid casual sex.
If you believe you have a moral duty to be the best person you can then passing up that opportunity in favour of the facsimiles is morally wrong.