@WiddlinDiddlin
Having a wheelchair in the car doesn't always stop it either.
I have had abuse hurled at me by two very vociferous pensioners (I know they were pensioners as they stated so, several times as if this should automatically qualify them) because I had taken the last blue badge space.
I apologised, initially thinking they had a badge, but we had simply got to the space first, we hadn't done anything sneaky, like nip in whilst they moved their car or anything!
They carried on, calling me a lazy fat cow, whilst my partner got my chair out, and eventually let slip they don't even HAVE a blue badge, just felt that blue badge spaces were also for anyone claiming an old age pension!
That is a really upsetting thing to go through - and hear about. Sadly though, as the OP and several others have said, I am not shocked by it. Same thing happened to a friend of mine when she bagged the last parking spot in the car park at a popular seaside resort last year. 2 people yelling at her that they were going for that one, and she said 'sorry but it's the only one and I do have a blue badge. Maybe another one will come up if you wait 5 or 10 minutes.'
The woman said 'doesn't look to be anything wrong with you anyway!'
(She has a chronic illness.) Friend just ignored her, and her mum said 'do you want to see her letter of confirmation from the specialist to confirm her chronic illness for her?'
The man just said 'chronic illness my arse. Just laziness.' 
Absolutely awful, and I can't believe people say this in real life. But they do. I know a number of people who have experienced it, and I have seen it happen when I am with someone who has a blue badge. The younger you are, the more likely you are to get attacked - by people 15-20 years older plus, because they think they have more of a right to a blue badge than you.
Sadly, as the pp I have quoted has illustrated, the couple who attacked my friend last year by the beach, were also 'older..' around 70-75, and like with her, they assumed their need and right was greater and more important, because they were 30 years older than her. They parked up eventually and ALSO did not have a blue badge.
I think a small number of people who shout at blue badge users for not looking disabled enough, or for being 'too young' are on this thread. 