Yeah, I see that argument a lot. I am a heterosexual man in a 28 year marriage in which we have not, and never intended, to "produce children".
So by your logic, my marriage is no better than that of two men.
Yes, indeed, your "marriage" is a fraud — had you honestly declared your intentions to whoever issued you the marriage-license, they would not (or should not) have issued one to you.
You are, of course, entitled to love, cherish, and have sex with whoever you please, but for the rest of the society to consider your union as something particularly noteworthy and privileged (such as marriage), simply living together and having sex is not enough. If the State has any legitimate reasons to recognize unions, instead of simply considering the union-members individually before the law, the unions must be producing children.
Go read about the origins of marriage
No, why don't you present the points you wish to argue, rather than send me collecting them for you?
which is more like slavery and men's property rights
That may be (or has been) the contract between the partners. Our argument here is about the society's recognition of the partnerships — whether or not to bestow the respect and the legal privileges traditionally granted to children-producing unions to all other cohabitating couples (and why not groups, BTW? or will that come later?) having (or having had at some point) sex?