The idea or concept all or most influential politicians have spilt innocent blood comes from the point of view all politicians are part of the system which allows ears and conflicts to continue going, it is a typical point of view from those who do not wish to think of politicians as individual humans beings, but as part of the gearbox of war.
It is very similar to people who blame all tax paying Americans for what is going on in the middle east and the destruction of the Gaza Strip, they disregard there are Taxpayers who also actively protest against what is going on in Gaza.
Politics as a profession is a mine field and a dirty game for the sake to climbing up to the top of the leadership of a country (the presidency), but I think it is unfair to put slightly debious politicians in the same bag with literal warmongers...