Hay, it's 8:00am so there's a good chance I'm sober.
@Justinslow, you may have noticed that your OP has taken a little incoming. Here's why.
Today I'll drive to work; a 16 mile journey along the A34 and A303. During that journey I'll see at around 10 drivers exceeding the speed limit by at least 15mph. I'll more than likely be dangerously tailgated at least once. I'll see, on average, two people on their mobiles. I could come home and start a post with the title "I saw an idiot in a vehicle", but I'd be starting a new thread on the same topic every single day. And that would get boring.
Threads like these usually have the assumption, sometimes explicitly stated, that the offending cyclist somehow shames the great tribe of all cyclists. This is textbook out-group thinking. This
TRL report has done the rounds on CC a few times over the years, but it's still worth a read. Summarising, an in-group will always regard any negative behaviour, however uncommon, by a member of an out-group as typical of that group, while excusing common negative behaviours within the in-group as exceptional or atypical. I give you 'the otherwise law-abiding motorist' coming to a magistrates near you today. In the end, "what people think" says more about them than it does the target of their thinking.
As Cain said in that great slasher potboiler The Old Testament, "Am I my brother's keeper?". Just because someone rides a bike, it doesn't mean we're BFFs. If they choose to put themselves in harms way by riding carelessly, RLJing or going into stealth mode, there's feck all I can do. Unlike driving, at least cycling is usually democratic enough that idiot behaviour only rewards it's perpetrator.
So I'm not going to flagellate myself because you've seen a Ninja.