You can say a show contains X, Y and Z bad thing, but firstly that doesn't mean it is there with intent to manipulate or change the thinking of the viewer. We know this isn't the case because of Seinfeld because it is literally the live events of Larry David: it is more a documentary of his and Seinfeld's life. So, while bad things exist in the show (and to what extent is hard to define) it's solely because that's how people actually live, not because there was any intent behind network executives to push an 'agenda' or 'perception' of how life should be. And we know this because they are tragic characters: they do bad things but nothing good ever happens to them. In fact, the writers and creators even acknowledged they were such horrible people the finale involved putting them in jail because that was what they deserved.

And, finally, the show was originally canned after the first season. They only made more seasons because the viewers themselves liked it so much. The network originally put it on at a bad time with a bad slot that would make most shows fail miserably: it was simply another show they made and not some attempt to force anything down people's throats. In fact, the show wouldn't have gone ahead if it wasn't for one of the producers who spoke up for Seinfeld extensively at NBC who is represented in the show as the man who comes to the comedy club and asks Jerry about making a pilot.

So, was there intent to brainwash the public? No, they didn't even really want the show at all, let alone to do well--it was happenstance and came from the people of NY.

Or, was there even a brainwashing message? No, after even a few seasons there are rarely happy endings for the characters with the rare exception of Jerry to contrast George, but even he has massive flaws that are constantly pointed at (germaphobe who cannot have a stable relationship). They even end up in prison to prove that point that they are not to be idolized.

Thirdly, did they even want to have a brainwashing message if you could even consider it that? No: every story came from the writers especially Larry David who based most characters around actual people in his life. Most of the events are based off of things he sourced (George's wife dies from licking stamps because he read about it in the paper, and they had wanted to kill off the character so used it--his apathy towards the situation is a reflection of George, who is just a hyperbolized version of Larry David).

Let me explain this to you: it is a sitcom. It is unrealistic. The events reflect the writers, but only in the most extreme way. No one is supposed to have good families or relationships because it is a COMEDY. Wether you are true or not is irrelevant because you are projecting.

You're basically saying we constantly need good loving messages all the time otherwise we'll fall into these horrible patterns. If we cannot have these shows without our society falling apart then how developed are we? This kinda thinking is debunked in like the first class of media studies: the hypodermic needle that whatever people consume changes them. If you can be so easily influenced by a TV show then the problem is not the TV it is you. People do not see a show like Seinfeld and want to engage in casual meaningless relationships: they already wanted to it's just Seinfeld made them feel it was more acceptable.