Not sure if serious

Have you ever had a game where you assumed that someone is joking around, but it turns out they were totally 100% dead serious about someone blatantly stupid?

For instance, I recently had a game where I was a Cho running top, initially against a Vlad. Obviously, this is heavily in my advantage, so the other team lane-switches to put their assassin in the top lane (Talon in this case) in the top and Vlad middle. Our mid is a Fizz and feeling fairly good about Vlad (for whatever reason) and doesn't want to copy the lane swap without having teleport, so we decide to sit on it and have the jungler make up the difference in top lane.

Maybe not the best tactical decision, but hardly a disaster, right? Our ADC disagreed.

But this story isn't be complaining about a bad ADC getting salty. The thrust of it is... the mid didn't do all that well against the lane-swap (and obviously I was countered at that point), and the ADC responded by accusing me of feeding the Vlad who was nowhere near my lane.

For obvious reasons of the map being right there on my screen, I assumed this was him joking around, and responded with basically "heh, cute". I didn't even realize he was genuinely that stupid until something like eight or nine chat exchanges had passed, at which point I sort of... gently hinted that maybe the map is a good thing to look at occasionally.

Pure, unadulterated rage. In end-game chat (we lost, albeit more from bottom lane getting rolled than the lane-swap issue) we got a continuing rant about how we'd have totally won if I hadn't fed the enemy that literally wasn't ever in the same quadrant of the map as me in the entirety of lane phase.

Am I unique in giving people in chat more credit for intelligence than they deserve? Should I just assume the dumbest possible speaker at all times?