What single words and idioms would best describe someone who loves to sit in judgment of others, almost making it a hobby to become a nitpicker. They are aware but un-acknowledging of their own deficiencies and of their non-eligibility as critics. They are overly critical of others, yet vehemently intolerant of any criticisms directed to them. I guess it is a combination of spite, rudeness and lack of insight. But they are not stupid.
As examples you could imagine an unaccomplished reality TV judge (I’m not sure what credentials they possess) being spiteful and mean. This may not be a very good example because sometime the judges put on a veneer of [this attribute] for ratings? Or say a colleague at work who feels threatened by your skills? Or a meddlesome neighbour perhaps who is jealous of your success?
Edit: Having considered the responses so far one apt overarching word I think is hostile, but perhaps there are better words or idioms? Another word that applies perhaps is caviling.