That was a good read.   It shows we have to careful to link a particular factor, (like owning shares or not owning shares), as having a causal effect on voting patterns.     I was surprised the preferences were as close as they were.   

Stock ownership is hardly an even playing field.   It's one thing to 'let it ride' in a retirement account hoping for modest retirement support.   It's quite another to have the extra income that gives you management/investment advice with the goal of creating wealth.   As in most things, wealth  increases your opportunites of success through mulitiple support structures, and this would include stock investment. 

I don't see any tax policy that changes that basic dynamic.   Government programs are hopefully designed to provide greater opportunity for those who would have very little otherwise.    It's why we've come to associate great wealth with 'privilage'.    Inequality of opportunity is a fact, not a statement of ideology.