I hate "common sense", and I can't help rolling my eyes when people use it as a justification. Common sense is little more than an assumption, it is the opposite of logic.

With common sense, the end justifies the means. Picture a Rube Goldberg machine that starts with a single domino and ends with a ringing bell. Common sense tells you that the end result of this process will be a ringing bell, therefore if you tap the bell yourself then you've achieved the same outcome, right? "That's just common sense!"

With logic, the means justify the end. In other words you look at the PROCESS and follow it to it's conclusion. You follow the trail of dominos and see they will knock a ball down a slope, that ball knocks a lever, and so on and so forth, until you reach the bell.

Yes they both result in a ringing bell, but logic would have showed you that part of the process involves a can of dog food being knocked over and into a bowl. Common sense just assumes the bell is the point based only on what's immediately apparent, and the end result of that approach is a disappointed dog.

"Common sense" is shorthand for "I'm making a reasonable assumption based on immediate evidence, rather than conducting an investigation to prove my theory." If common sense was actually the be all and end all some people seem to think it is, framing someone for murder would be a hell of a lot easier. No need to check for fingerprints if Bob's name is engraved on the knife handle and everyone knows Bob never liked Dave very much!

Research, evidence, and logic will get you an answer, common sense will get you a reasonable assumption. And that's why I don't trust people who use "That's just common sense" as a closing argument.