I don't know of a single leftist who would call Gates a leftist. Liberal, perhaps, in the economic and social sense, but not a leftist in any way shape or form. I don't know why its so hard for people to distinguish between these two very different groups.
Blame Rush Limbaugh and others for conflating them in the 90s.
I don't know if people generally know the difference before that, but personally it's only been recently that I've been exposed to sources that distinguish between left and liberal.