You haven't explained why apparently contradictory advice is a bad thing.
This doesn't make any logical sense to me. "Apparently" contradictory means that it may or may not be so there's nothing for me to explain. The problem with things that are *actually* contradictory is inherent in the definition.
Different situations call for different methods/approaches (as do different audiences).
Yes, but in general you have to establish what those initial conditions are. "Next time you roll dice, do X'. vs. "Next time you roll dice, avoid doing X." You could argue that the two recommendations were meant to be applied to two different circumstances, but then I think that should be made clear - otherwise the advice just becomes a Rorschach test for what you want it to say.
And indeed, many people on this thread have seemingly just chosen which bits of the advice to pay attention to and said that the rest was "out of context", "baldy written" or whatever. But then I have to wonder what the point was. Seems to me to be just folks who want the opinions and experiences validated that they already have - and those aren't newbies.
Take 'railroading' for instance. It's something that usually should be avoided, but, depending on the group, can range from 'occasionally tolerable when the alternative is worse' to 'practically demanded during every session'.
Ok - well, how is this an example of inconsistent advice? Your example might be too vague (perhaps appropriately for what you intended) for me to have much of an opinion about it - and by virtue of that nothing seems particularly contradictory since you allude to different initial conditions or circumstances.
They clearly intended the 4e DMG to explain how to DM, even for those with no prior experience. The fact that this is seen as a novel approach, in 2008, by the 4th edition of the rule set, says a lot about the some curious decisions made by previous designers of the game.
My recollection is that the scope of the 2E and 3E DMGs were about the same - they weren't "advanced" books IMO. I don't find it particularly novel in 4E, it's just that they're rehashing the same-old stuff. In any case I'd think there are large numbers of people that could have dispensed with the DM advice stuff in favor of more crunch.
How would you write the DMG otherwise?
I don't need to take a description of the various player types with me to my next game. I do need the rules for mounted combat. I don't want to see the same player types discussed in 5E and 6E just because I need the mounted combat rules. The advice should and could be seperate from the crunch.
In fact, if it's all that important to the health of the hobby that people understand this stuff, then they really could post it on the web for free. A good chunk of the advice given was actually derivative of other things I've read elsewhere on the subject anyway, so it's not like they're giving away a lot of unique intellectual property. Just seemed like they were trying to round out their term paper to the requisite number of pages.