Should we, the consumers only purchase from companies who have public responsibility?

Your definition of "public responsibility" would be helpful here. Perhaps you mean "corporate social responsibility" as defined by WIKI (link below). In this matter you may buy from whoever you want, but to be rigorously straightforward. you would have to give up a great number of inexpensive-to-buy products/services which use nasty old petroleum in some form, nuclear energy for power, use materials ripped from the Earth without regard to the ecology of the planet and force people to work in poor and hazardous and ill-paid positions, the latter two conditions especially obtain in 3rd and 2nd world nations.