Can it be that Red and Sony have the highest scores and Canon sensors much lower
and DXO data therefore should not be seen as reliable?
DxOMark Scores ≠ DxoMark data. Can you explain exactly how their measurement data are used to generate the scores? No, because they don't publish that information. In the case of lenses, the measured data on optical performance have almost nothing to do with the Scores.
As I've stated many times, their measurements (= data) are useful, although occasionally wrong, but their Scores are biased and useless, i.e. not reliable.
Several peoples approach to DXO seems to be negative as long as the Canon does not get high sensor scores
Perhaps, but speaking for myself, my opinion of DxO's Scores is negative because they are biased and determined in an unknown manner. While their software is excellent and their measurements are generally well done and useful, they are not perfect. Their data are sometimes flat out wrong, e.g. their conclusion that the original 70-200/2.8L IS is better than the 70-200/2.8L IS II. More damning to their credibility is the way they handled their error - they denied that there was any mistake, but subsequently and silently modified their data to reflect the fact that the MkII version of the lens is better.
The honest thing to do when you make a mistake - whether in a lens measurement or posting a quotation out of context - is to own up to it, and correct it openly. A person or a company that denies wrongdoing and obfuscates the issue does not deserve respect.