Basically, this states that if you input false data, you should expect an incorrect result. That is quite true here. Which is why you should always double-verify data before posting it to a diary.
2. Be liberal in what you accept, and conservative in what you send.
This particular piece of advice comes from the need to write networking or client/server software that plays nice. Basically, you can't trust what the other side will send, so you have to be tolerant of errors and deliberately malformed data (this, by the way, is a primary cause of security holes in Microsoft software). On the flip side, you should only send out things that you know fit the specification rigidly, so that the program on the other side has half a chance of dealing with it correctly.
This actually fits quite well with this community, as a primary cause of flamewars, ratings wars, etc., seem to be caused by people being conservative in what they accept and liberal in what they send. It's bad practice in programming, and it's bad practice on DailyKos. If you don't like what someone has to say, rebut them politely or ignore it - don't go downrating them (if their posts otherwise don't fit the criteria) or responding with incendiary rhetoric. It doesn't help.
3. When debugging a program, sometimes you have to examine its internals, and not just look at its inputs and outputs.
This fits pretty well with progressives in general. If you look at the inputs and outputs to the present administration and its toadies, you'll be confused and you'll resort to patching - basically reacting to problems instead of fixing them. You have to look at their basic motivations and between the lines, at the things they don't want you to see - only then will you discover the root cause of the problem and be able to fix it.
4. Sometimes code just needs to be rewritten.
There are times when I look at some code that someone else wrote - or even that I wrote - and decide that it will be much easier and more productive to scrap the code and start over than to try to deal with the mess. Same applies here - sometimes you just have to get rid of the troublemakers and start over, no matter what kind of "good" things they claim to accomplish for you.
5. Always have a good specification.
In code, this means that you should design the code before writing it. In politics, this means that you should have a good platform and a coherent set of beliefs before running for office, and before trying to debate with the person opposite of you on the political spectrum. Code written without a specification tends to come in over-budget and of low quality. Political campaigns seem to have the same problem. Imagine that.
6. Sometimes it's good to vent.
There are times when I have been fighting with code for a while and I just feel like throwing the computer across the room. At times like that, I find a nice IRC channel or something and start virtually throwing things. Sometimes people need to do that, even if it's just typing hard. Try to be understanding of people who are venting - better that than the alternatlve. Remember Melvin and his stapler? But when you're done venting, it's important to shut up and get back to work. Same applies here.
7. You can't choose your coworkers.
Nor can you choose your political allies. You can, however, choose how you deal with them. Be nice, courteous, and professional, even if some idiot is troll-rating you for no reason. It speaks volumes for you, and puts his behavior into even starker relief against yours.
8. Listen to criticism.
When coding, you may know a lot, but someone always knows more than you. Same with DailyKos and politics. Listen to them. You don't have to agree, but even listening can help you see things in a different light.
Hope this helps. :-) Maybe it's a stupid diary, but I try to write what I know. I'm no political maven, but there are different life lessons that can apply to DailyKos and the wider progressive community. Maybe I'll find some about pianism too...