I should think his aversion to vinegar in his pub, is because it could give rise to vinegar flies, aka fruit flies. As one of the best methods of trapping them is a 'beer trap', I imagine they would adore a pub cellar.
Most modern vinegars are so refined and pasteurised that the occurance of a 'mother of vinegar' is highly unlikely. However this growth can turn any alcoholic liquid to vinegar, and I assume that he may fear cross contamination, should such a beast arrive with his vinegar supply.