In short, there was a multitude of reasons for the creation of the Electoral College, and it is somewhat misleading to present the reason as appeasement to Southern slaveowners.
I see a multitude of arguments, but not a multitude of reasons. What you’re citing could easily be dismissed as propaganda. Maybe some of it was genuine, but it was hardly the impetus for the electoral college. The reality of the situation was as Madison described — the Constitution was not going to get ratified without making concessions for slaveholders and the Southern states. It was going to be a bust, and that was evidently a highly undesirable outcome for Northern statesmen who desperately wanted a union of all the states.
None of these ideological arguments had the political force of the Southern states who were going to simply refuse to cooperate if they were not placated. In order to make sure the electoral college and Three-Fifths Compromise went through, it comes as no surprise that political rhetoric was employed to get Northerners to accept what was essentially a raw deal for them. None of these people and their alleged ideologies about the electoral college formed a powerful bloc the way the Southern states and their naked self-interest did. None of them were threatening to scuttle the whole deal without an electoral college, but the South was, and it was fully capable of doing it.
If there were no slavery, there would have been no Three-Fifths Compromise, and the likelihood of an electoral college having been created would have been enormously diminished. These are there because of slavery. It is no accident the electoral college was formulated to precisely mirror the calculus for assigning representatives based on the Three-Fifths Compromise, and the Three-Fifths Compromise was 100% about placating slaveholders.