Runs in the family. I just got done arguing with my mom about why I shouldn't have to repeat the words "I love you" to her like she's the American Flag. I digress though.
No drama. If you look at it with an open mind, he's just trying to educate. How does a teacher teach a student if the teacher isn't allowed to bring a point across with factual information?
And I can't say he takes anything like this "seriously" in that way. He is indeed serious with the contents of the response, but there's no tension or the like within it. Lastly, this is hardly something anyone in my family could be stressing themselves out with, especially considering how we work lol.
Having known Slasher for almost 11 years now (still not as long as you though, family hacks) I would pretty much say this.
He's not upset with you or attacking you Shulk, it's just his way of trying to get points across. Nothing like this should cause tension for him or anyone else. If anything, he's just being a taurus and you don't need to get too worked up over it whether you agree with him or not. He just likes trying to prove his points sometimes :P
Also I think this thread is hilarious. Spin, you and your advanced computer shenanigans.