Gordon,
Whilst I agree with much of what you say, in terms of idiots causing disturbance and the fact that in places like Uist in some areas Schedule 1 birds are the typical relatively common species which do interact regularly with people, you should be careful what you repeat as 'word is' and 'I believe'.
The historical issue regarding Schedule 1 photography licences dates back to a number of incidents where these were abused or suspected of abuse, therefore the safest way to deal with the situation (where evidence was often circumstantial) was to stop issuing licences, however, after a suitable gap one or two licences have now been given to individuals to carry out photography. The process does involve checking on whether the persons applying are considered responsible so it's not unusual for local staff to be contacted about either the person or which species and where they wish to photograph.
The golden eagle eyrie you mention is not an alternative site for the pair where the watchpoint is, and has not been a successfully used site for many years - 'shifting' birds as soon as they start building a nest is an offence so I doubt that is what the RSPB did. Incidently, there is currently a consultation going through the Scottish Government which may make it an offence to disturb golden eagles (and some other species) full stop and doing anything at or near a nest outwith the breeding season.
Schedule 1 disturbance licences are usually area and/or species specific, so the person you mention would have known that they were breaking the law if they had a licence covering Lancashire only.
Technically, what you said about the peat-cutter is correct however, there's a difference(although technically not legally) between someone cutting peats, who is by and large not interested in the birds, (which are as you suggest habituated to the people doing this - they've been cutting peat there as long as the birds have been nesting) unless they are in the immediate vicinty of a nest causing disturbance (would be reckless disturbance), as opposed to a birdwatcher/photographer who goes over there to find and photograph birds at or near nests (deliberate and if they know anything about birds and legislation, illegal).
I would think you would find some common sense applied by the authorities to some of the 'technical offences' mentioned in the thread. Taking photos of avocets from a hide on a nature reserve ain't going to get you prosecuted in reality.
Behaviour of birds will generally tell you you are too close, so if you are a birdwatcher or claim to be a bird/wildlife photographer you should know if you have overstepped the mark - so if a witness tells the authorities that harriers were flying around agitated, calling and mobbing the person then they're wide open to prosecution (the acceptance level of tolerance of individual birds will vary but the birds only respond when they decide you are too near for them to tolerate you).
Digital photography/digiscoping should have made disturbance issues less due to the fact that photos can be taken from non-disturbing distance more easily than ever, however, as has been debated several times particularly with vagrants, a number of people want a frame filler at all cost (news of snowy owls here has been suppressed at times due to excessive disturbance by people with cameras and deliberate flushing of the birds to get flight shots), and that happens too with rare breeding birds - seems for some to be almost a competition to see who can get the 'best pic' on web.
The real difficulty with digital photography is it is pretty much impossible to know whether an offence has been committed (unless you get things like the exif data).
Incidently, the Committee Road isn't an 'official' watchpoint as such, but it is a safe area for visiting birdwatchers to watch/photograph a number of schedule 1 species without causing disturbance and as you say there is no need to go off the road to be able to get good photos as the birds are relatively tolerant of people - the small car park is a relatively recent local access initiative partly to prevent the single road passing places being blocked up (technically a motoring offence), given the number of birdwatchers who visit there now in spring.
As for the Schedule 1 list being out of date - this is partly a legislative quirk - the Schedules of the WCA 1981 for animals and plants have a 5 yearly recview built in , Schedule 1 for birds does not. For changes to be made to Schedule 1 a separate review has to be arranged involving the country agencies, JNCC and Govt - changes can be made, capercaillie was upgraded to Schedule 1 relatively recently.
Cheers,
Andrew