I think he's saying that someone here illegally should be able to return to country of origin and then re-enter illegally at will, protected from repatriation. This puts a premium on entering the country by whatever means and at whatever risk.

He was saying that being married to a US citizen should not enable a person to enter the US legally. (He said "sleeping with", but in fact the US does not generally grant dependant visas to unmarried partners.)

Not quite, I'm saying that from a utilitarian perspective, importing wives for US citizens is not better for the country than importing high skilled workers.

I'm also saying that from a justice perspective, banging an American and getting him pony up for marriage doesn't make a person intrinsically more deserving of citizenship than working hard and creating (potential) value for the US.

Again - I'm generally an open borders proponent. What I say we should do is stop using violence to prevent peaceful people from entering the US and engaging in trade here. (And we should make whatever economic adjustments are necessary to prevent an increase in state-induced violence/threats of violence, e.g. eliminate the welfare state.)

But if I accept the logic behind restricted borders (e.g. "we can't handle too many more" and "immigration should benefit natives"), that logic doesn't really support nepotism based immigration.

You appear to be very cynical about marriage and relationships in general. Visas are granted to the spouses of US citizens because the US recognizes the right of these citizens to have a family life. It is not only the spouse who is harmed if the visa is denied but also the US citizen in question, whose rights the US government is obliged to recognize. Utilitarian considerations are largely irrelevant. As far as justice is concerned, I don't see why you think it would be unjust to grant visas to spouses. Of course spouses of US citizens are not the only people who should be granted visas, but no-one suggested that was the case.