Ok, it's pretty easy for you to see that doing good is better than doing evil and rationalizing you are doing good, right? Because after all, you are doing good and not evil.
So the question comes down to what is worse, doing evil and acknowledging you are doing evil or doing evil and rationalizing you are doing good, right?
So of these two, doing evil and acknowledging that you are doing evil does not glorify doing evil. Whereas doing evil and rationalizing you are doing, right glorifies evil. It's literally how slavery and Nazism was allowed to spread. By pretending that evil is good. No one is going to get on the band wagon to do evil for the sake of evil. Lots of people will get on the bandwagon if you convince them evil is good though.
Now do you understand?