“But if hospitals have such rules [against same sex partner visitation] a thing I find hard to believe in this PC-whipped age.” Try again. Gay man forced out of dying partner’s room at Oregon Health and Science University hospital. This is from a week ago. A woman in Florida, carrying documents, was kept out of the room while her partner of 18 years died. While their children stood by, no less. Why do people continually bury their heads in the sands about these things? “Oh, I can’t believe that people are so cruel!” It happens. We know it happens. We have documentation that it does. You know what stops it? The universally-understood bond of marriage.
The other major flaw with your argument is you never explain why extending marriage rights to gay couples will “mess” (with), “redefine” “overturn” or “overhaul” marriage. You simply assume your argument throughout.
When marriage changed from a property arrangement between a father a prospective husband, when women were changed from essentially chattel to equal partners, when marriage was changed from multiple wives to one - all of these did far more to change marriage then changing the gender of the two people involved in today’s civil marriage laws.
Last - “people who want to marry their ponies, their sisters, or their soccer team?” I thought equating homosexuality with bestiality and incest was limited to the religiously motivated. Disgusting. As for polygamy - marriage used to be that way in many cultures. Perhaps you had better ask historians why we changed away from it rather than ask the gays why they should have to preemptively defend against something for which they’re not asking.