Signature verification has a low accuracy and is prone to mistakes. Its not a reliable method. What is worse is that it tends to discriminate against those who have a different native language or those who have mental disabilities.
In my opinion its a method that shouldn't be used at all.
In general i think you are right about the egocentric and morally abhorrent behavior of politicians, however i would suggest that you have a too positive view of the other side. I don't believe there is any big difference. There is though a bigger predisposition to commit crimes for those having left leaning sympathies. Not drawing any further conclusions on that.