Killing Is Wrong
A simple answer to complex problems, good for many political debates: Killing is wrong.
Use liberally when discussing abortion, Islamic fascism, euthanasia, gun control, capital punishment, etc.
For example: "Killing is wrong, therefore good people need to carry guns to protect themselves from bad people who otherwise might kill them."
Or: "Killing is wrong, therefore if you kill somebody, you forfeit your right to exist."
It's true that not all debates can be argued this way. For some, you'll have to revert to "All men are created equal" or "humans are more important than other species." But those aren't as definitive, so try to stick to arguments where you can use the "killing is wrong" slogan.