It is not so much that RET does not make sense, it is that they start with the conclusion that the earth is flat and work backwards. RET is either a misinterpretation of the flat earth, or it is a hoax that some cabal of global conspirators have created to trick people into thinking the earth is not flat. To the FETer, evidence is something to explain. True science makes predictions and creates experiments that can prove or disprove a hypothesis. A big hole with FET is that every time they try to explain one observation, the explanation does not work with other observations. At this point it is time to call in the conspiracy or just claim it is some 'bendy' effect of light or some such non sense.
Part of the issue is the nature of language. Most words have multiple meanings and subtle differences in connotation. Take the word free for example, Merriam Webster has 15 definitions:
http://www.merriam-webster.com/dictionary/freeSo the term 'free thinker' can be interpreted many ways. Free thinking in therms of FET amounts to 'worthless thinking'.
The confusion comes in when they claim someone who accepts RET is not a free thinker. Somehow there is a leap of reason that makes that claim self evident to the FETer. But there is a great amount of freedom in RET, one is free to test any and all claims and if something is found to be incorrect and can be demonstrated, the results will be added to the sum of human knowledge. One is even free to let go of any concept of shape and look for a model that better fits what is observed. FET is not free, it does not allow for the 'fact' that the earth is flat to be released. It is an odd free speech dogma, a construct that says the individual is as good of an authority as any, and as such they are free to hold "a point of view or tenet put forth as authoritative without adequate grounds (
http://www.merriam-webster.com/dictionary/dogma)".
The reason I provide a link to the definition of dogma is because I need the authoritative definition if I am to be understood. Authority is not always a bad thing, and it is required for communication with human language. People can and will abuse authority, but without it we are cavemen slugging it out in the muck.