I think the standard counter to this is that, if it can be reasonably assumed that you're not welcome to do it and if you're not being entrapped, then the ease with which a crime is committed should have no bearing on the severity of the crime. Stealing someone's car doesn't become moral if the person leaves the car unlocked and running, even if it "only" involves opening a car door and driving a car. I don't see why computer systems should be different.

However, breaking into someone's car in order to roll up their windows and leave them a note telling them not to do it is perfectly good in my book. So I think it's better when people focus more on the severity of the actual crime committed, rather than on the ease of committing it.