>First, every negative thing you mention there happens all the time, and it's done by straight people in heterosexual marriages. Where's the gay connection?

There isn't one. You asked what the downside was to deleting legal marriage entirely.

>Edit: Also, your Wikipedia link actually backs up my argument that marriage has historically been a religious institution, so I'm not sure what you're going for there, or how it explains why the government needed to get involved.

You said that "only recently" had governments started supplying benefits to married persons. This is false. As Wikipedia shows, there was legal recognition in various jurisdictions from ancient times. If you mean to say that there are few instances of purely secular marital law until recently, then sure, but also note that until the American Revolution there were few states without an officially-sanctioned state religion, so the religious tradition and the enforceable legal body may not be separate. Israel, for instance, enforced law related to marriage; adulterers were prosecuted, etc. etc. Likewise throughout history. Here's a whole page on "Ancient Greek Marriage Law", indicating non-recent legal recognition of marriage: https://en.wikipedia.org/wiki/Ancient_Greek_marriage_law

> > First, every negative thing you mention there happens all the time, and it's done by straight people in heterosexual marriages. Where's the gay connection?

> There isn't one. You asked what the downside was to deleting legal marriage entirely.

So there's a downside to deleting legal marriage entirely. So there must be some smaller downside to disallowing it partially. Why are you for that downside?

Because I don't believe homosexual coupling is good (for reasons listed elsewhere in this thread), so I don't believe that the government should promote it. As I stated originally, it's not a forgone conclusion that the reasons we want to promote heterosexual coupling are not necessarily applicable to homosexual coupling.

I do believe that heterosexual coupling is good, and I believe that it's good for the government to accept that marriage is a near-universal practice and its implementation may be codified officially in law and modified by nuptial contracts where applicable rather than leaving the whole thing blank, waiting until a legally illiterate spouse because widowed and/or abandoned, and leaving that person with no recourse against the abandonment and/or death, mechanism to gain control of shared property, etc. I think it's debatable whether the government should be in the business of providing less crucial incentives, like tax breaks, or whether that operates best as a non-governmental function.