As a controller in the UK I have seen this situation before.Aircraft divert due to the Vis below Cat 1 limits and then the vis increases.I have told the pilot the improved vis,but they always continue to divert.They must be on diversion fuel by then.Quite often the RVR has gone down again,so if they got caught up in any more holding,it could develop into an emergency situation with fuel shortage.
Not condoning rude R/t which is always unprofessional.