If you want to know how and why filtering (what you call "adjustments" ) is done, you should read a book on data assimilation, such as Atmospheric Data Analysis by Roger Daley, or Spatial Objective Analysis by H. Thiebaux. The mathematics can be pretty hairy, though. At the very least you should try and learn what the problem of "representativeness" refers to, that would probably go a long way toward you understanding what's going on.
Just because you don't understand something doesn't mean that there is anything dishonest about it.
EDIT: You say:
"Sorry, not buying the arguments from the True Believers. I DON'T trust adjusted data. Deniers like myself have been proven right that the methodology of how they make their adjustments are severely flawed."
I recommended reading some books so that you would understand why "raw" data is not used, but since you choose to reject knowledge and wallow in ignorance, let me clue you in on something in science: every piece of data, whether you know it or not, has been filtered. Just how do you think any sort of global "temperature" could even be defined without "adjusting"? There is no thermometer that measures a single temperature for the planet, in case you didn't know.
In fact you don't understand data, flawed or otherwise. You know nothing about the field of data assimilation, so you choose presume that people lie about it because you don't know what they're doing.
Deniers would rather remain ignorant and claim fraud rather than actually taking the effort to learn something they don't understand, what a bunch of idiots.