YANBU in thinking a little bit of sugar won't kill.
But YABU if you think sugar is not like booze and tobacco, re not needing it and re the dangers of consuming to much of it.
The problem with refined sugar is, (like re alcohol), the question of "what is moderation"? (And "what is too much"?)
No-one actually needs to have refined sugar in their diet at all, as long as there are 'better' foods available eg (mostly) unprocessed veg/meat/fruit/nuts/cereals & good fats.
So why shouldn't we all aim for a zero (refined) sugar target? (Hard to achieve as sugar lurks in bread and all kinds of not obviously sweet food goods.)
Alcohol & tobacco were probably much more heavily consumed per capita before refined sugar became so cheap and available. (Or am I wrong?) So, (cheap), sugar is a relatively new, (and insidious), arrival in our diet? Cos we have gone mad consuming it!
Refined sugars, (especially high fructose corn syrup, aka HFCS), can be considered (by biochemists & metabolsim experts) to be a poison/toxin. So that's why a lot of people are now trying to avoid refined sugars, as much as is possible.
Of course, small amounts of poison can be tolerated but there is a cumulative effect. (Habit forming and sustained exposure can easily lead to significant health problems. Also not so good for teeth.)
So if people do not want a free doughnut, it's like saying "no thanks" to an offer of a free ciggie or a free beer at work. And. maybe they eat at fixed times and are not hungry/don't want to take on empty calories?
So (next time) just smile and understand if some (or a lot of) people don't want a doughnut. They probably are just thinking of their health?
Majority of British people seem to struggle with maintaining a healthy weight and eating enough veg/fibre so offering round doughnuts is not really a kind thing to do? (Especially as some folks have a low threshold to temptation?)
So it's like giving a loved dog some chocolate? (They will like it but it isn't good for them!)
And why teach your kids that doughnuts are "a treat", thus setting up bad habits/associations for their future?
If sugar was really a rare treat then it wouldn't matter. But wouldnt be 'good' either. (Our sugar consumption has risen year on year. And we nearly all consume far too much of it.)
A banana is better (for your health) but too many bananas are also
bad (too much natural sugar) and too much of any type of food is bad as can lead to obesity.
So there is no perfect food to give away IMO. (Cos most of us eat too much anyhow.)
Overall, YABU to think people should always accept a free doughnut (or whatever you have to give away), however kindly it was offered.
They shouldn't be rude when they refuse an offer though. A simple "no thanks" will do, as long as you don't then say ... "Why? Are you on a diet?" and/or "Go on, just have one!" .... which is always VERY annoying! 