If someone is wrongly reported as being drunk however is actually having a complication because of his/her diabetes, what's the difference? If he's driving erratically, it doesn't really matter if it's because of alcohol or diabetes, someone needs to pull him over. Someone who can't control his diabetes properly shouldn't even be driving in the first place... Would you want a pilot with a heart condition to be piloting an airplane if he was the only pilot on board? In regards to the tweet of him being drunk, even if he wasn't and it a problem related to his diabetes which caused him to drive this way, I would say it was still irresponsible on that person's behalf.
Second, in regards to "being convicted of a DUI without a breathalyzer", that really sounds suspicious... Do you have any actual proof to substantiate that claim? Maybe what you meant was "you can get charged even though you're not above the .08 limit". If that's the case, than yeah, you're right... I don't recall which one is which, but there are two different charges which are quite similar. One of them means you were driving and legally drunk (i.e.: over the .08 limit) and the other means although you didn't get a fail, you were still impaired and exhibiting signs of it.
To tell you a little bit about where I live... The machines I've seen in use (and I suspect this is the norm) usually have 3 results: pass, warning (between .05 and below .08) and failed (.08 or more). It use to be that, you could hit "warning" as often as you wanted to. There wouldn't be a mark on your record and you would simply get a 12hr suspension. After some time, they've noticed the same people over and over again getting "warning". What did they do about it? Now, they keep track of people getting "Warning".
First time caught with a warning: license suspension for 3 days
Second time caught: 7 day suspension, driving school for drunks
Third time caught: 30 day suspension and they force you to go into an alcohol treatment program.
The information stays on your driving record for 5 years. Is it harsh? Perhaps. Lots of businesses weren't happy with the decision! (upscale restaurants serving wine, clubs, etc..) however that's what happens when a few people screw it up for everyone else. I'm quite ok with these new laws...
One last thing.. I agree with you that cops probably have more pull than they should to stay out of the spotlight for stuff like this, however this doesn't mean we should make the laws more relax for everyone else. You're simply looking at this backwards.