I agree that another argument outside of religion needs to be used against the gay lifestyle.
1) It is unhealthy. The average lifespan of gays is extreemly short. The same people who carp about smoking and McDonalds are being hypocritical.
2) It is "unnatural". The best line I've seen on this is from Dr. Laura who said "Penis, Vagina, what is it that you don't understand"?
3) There are innumerable studies that say that children need both a father and mother. And even if the "family" doesn't intend on having children, the example set that male-female couples is the "proper" family is good for the community. If others want to break these traditions, fine. But let's not encurage it with social custom.
Why not apply that same logic to abortion and keep religion out of it, if for no other reason than to keep the lefties from screaming, "Religious zealot?" When a leftie asks about abortion just reply, "It's not reproductive and is not in the best interests of bettering the human race." That should silence anyone.
This is even easier.
1) If it is important to give rights to all people. Then it is equally important to give rights to unborn people as well. The Constitution does not discriminate against unborn people.
2) Roe vs. Wade is just bad law. There is no legitimate Constitutional right of privacy that allows the Dr. Patient relationship to do anything it wants. Hell, we don't even allow Doctors the "privacy" to prescribe many drugs. And in that case there certianly is no third human involved. Dr. Kevorkian didn't have the right of privacy to conspire with his patients to kill them. He ended up in jail.
3) People might argue the merrits of abortion, but Roe sets a bad precident that the courts can just make up law. I would think that this would be anathema to good liberals, because some boogyman like John Ashcroft could come along and do real damage against them by bypassing the Congress and getting 5 justices to do his bidding.
4) If the Constitution gives the right to marry anyone they want simply because this makes them happy. Then it is certianly within the same argument to say that poligamy and polyamory should be allowed as well. When pro-gay marriage people insist that this isn't the case they're being hypocritical. And they're praciticing religious biggotry against the Arab and Mormon communities that want this practice recognized.