I'd just like to say, I really enjoy all the drama you guys constantly create. It's far more interesting than what happens on the srk thread. However, I don't like reruns so I'll just give a point of view that no-one cares about in hopes that this ends swiftly and we can proceed to new kinds of drama.
PC, much as I luv you, I'll have to stop you and tell you that you're in the wrong here. As joker said, just because someone's not picking their main against you doesn't mean they're not playing serious. After all, the point of casuals is to improve all aspects of your game, not just one specific area.
I'll lead by example. As only blank knows, I've played Akiha since MBAC. When MBAA came out, I stuck to my roots despite all the changes and stuck with C-Akiha since she plays the same. However, due to matchup problems that remained since MBAC (****ing nero), I was forced to rethink my decision to play C-Akiha exclusively and find some way of dealing with her weaknesses. When I trained with blank, I didn't see my C-Akiha improving that much so I looked for alts. Don't remember how I ended up with F-Satsuki, but she ended up complementing my playstyle better than C-Akiha and my skills with her soared to the point that she became my main and has done me very well since the switch (a lot better than even Akiha did for me back in MBAC days... which is saying a lot!).
tl;dr - Secondaries are a means for someone to deal with matchups, sure, but also a means for a player to re-evaluate themselves. If you don't play seriously against their secondaries, you may be denying them of this and their skills may stagnate.