I'd rather not spoil my run by actually dealing with abuse personally, so by and large I ignore it.
However, there have been (thankfully) rare occasions when it's got either a) irritatingly persistent or b) very unpleasant.
Then if possible I might run directly at the source - that usually makes them panic! and I can pass on my way. Absolute last resort is spitting - either down on the ground not too far away from the source, or, in the case some years ago of the smart@rse who chose to run alongside me shouting "die you b@st@rd! die you b@st@rd!", straight at him.