Several years ago, my colleagues and I attempted to get a small paper published, it was rejected and we ran out of time - and as it was a 'side-project' type of paper, we left it at that.  We thought that was the end of it - this was not the case.

One of the reviewers who made themselves known to us wrote some pretty terse messages to us about his disagreement with what was a relatively minor point.  We graciously took his feedback as he is an established (published) researcher in that field. We moved on to different fields - which this reviewer has no published work in.

What has been happening since is that he will write an email questioning every single paper that I get published, not deliberately being insulting - but not offering anything constructive nor asking for clarification of the content etc.  He has admitted that what I research is beyond his area of expertise - his questions are more in the vein of 'Are you sure you did enough testing of X' etc.

How do I deal with this persistent 'academic stalking' while at the same time, not make a 'fuss'?