So basically you're complaining because you feel that SE's customer service script is condescending? Because that's what this is; 'Have an AWESOME DAY' is, I guarantee you, either what they are required to end every single contact with (most likely), or one of several possible contact enders that they are required to use.

That's how customer service works in most professional companies; you're given a 'script' to follow and you must follow it or face discipline, even in cases where it ends up being wildly inappropriate in context; for instance, when I used to work for a major time-share chain, we were supposed to end every call with 'my pleasure'. This was absolutely hilarious when you would end a call with a customer positively livid at you and the company (Which was quite common during busy season).