I'm a doctor in the US, and I'm stepping into the line of fire here as there is some serious doctor hate going on in this thread, but here goes...
First of all (in the US at least) most of these arguments are moot because patients by law have the right to their medical record. So, regardless of what your doctor thinks, by federal law you have the right to request and get access to your medical record.
In regards to the attitudes about IF patients should have this access I would be willing to bet that older physicians would be more against it than younger physicians. Doctors above a certain age tend to be more paternalistic towards patients than younger doctors.
My personal opinion is that any individual should be able to obtain access to their own medical notes.
However, most people are not familiar with the diagnostic process and jargon used in medical records. This could definitely lead to misinterpretation or confusion by a patient or the feeling that information was withheld when that is not the case at all. For instance I may write in a chart "left lung cavitary mass - malignancy vs TB vs fungal infection" indicating that I'm not yet sure what it is and more workup is needed. Do I tell the patient every possible differential diagnosis? No, because that tends to freak patients out, I say "I don't know what it is yet, we need to do some more tests."
If the patient read my note without understanding how to interpret it they may feel that information was withheld or the doctor has no clue what's going on.
I think that is more what is behind the results of this survey than doctors "covering their ass", because if a patient wants to sue they will sue, and every single piece of information about that patient will be subpoenaed and scrutinized by lawyers. You cover your ass by putting complete and accurate information into the medical record, and not trying to cover up mistakes if they happen.
Personally I would not care if any of my patients read their chart. I will even show it to them "See, last time I wrote that this was going on, is that still a problem?"