Wow I didn't realize there was such violent debate about this. Are you aware of any evidence that he knew he had AIDS and tried to give it to others? some people directly say he didn't know, e.g. Edmund White:

He himself wasn’t sure what his illness was until the last few months (he died in 1984). He was horrified at the thought that he might have infected his partner but fortunately he hadn’t.

In my cursory search, claims that he was deliberately infecting other people seem to come from one book, The Passion of Michel Foucalt. John Knoblock sums up the opposing view:

Foucault was in Berkeley only in 1979, 1980, when no one knew about the epidemic, and in the spring of 1983, when he was not yet ill. When he became ill in the summer of 1983, he thought initially that his persistent coughing was a pulminary infection which get better "as soon as I am in California." His experiences in California in the fall of 1983 are not well known, and those in a position to know--which means a very small number of confidents in the French department there who shared his tastes, suggest there were few experiences. James Miller assembles what gossip he could find in an effort to test the idea that Foucault deliberately infected others, but concludes that the answer "may never be known" because there is very little evidence, and what there is is contested by people in a position to know.

Much more willing to believe charges of pederasty, Allen Ginsberg style, without investigating. But intentionally spreading AIDS is pretty unusual.