The problem comes when I act as if I am certain that my policy proposals are better than yours - and, worse, that you are therefore evil for proposing such flawed policies as you do. We assign to policies a certainty that they don't deserve.
"In reality no political program can be more than probably correct." - C. S. Lewis.
Even then, there is generally agreement that murder is wrong, and that murder means killing innocent people. The disagreement is generally over what constitutes "innocent" and "people". Similarly, pretty much everyone agrees that stealing is wrong, the differences are just in the details of what constitutes property and associated rights.
"I believe I have a moral responsibility not to wantonly slaughter my neighbors."
It's a short sentence, but the amount of waffling in it is amazing.