To be this hacked off at the MIL?!

[Madeaminnieme]

So we all know there's this craze for the fidget spinners just now.
I was in my MIL's last week and the discussion came up about them. I said my 6 year old DS's school was only allowing them for this kids with attention issues as they were designed for and because of recent injury reports plus the fact there is nothing wrong with my DS's attention I told my MIL wasn't buying him one. I said I didn't want to fall into the trap of buying him any new craze every time they came up incase one of them was something we couldn't afford. I was also concerned about the injury's being reported.
I've nothing against other parents getting their kids one but that's how I feel.
Anyway, this week for whatever reason, my MIL wanted to get herself one and also got one for my DS.
AIBU to be hacked off that she disregarded what I said and gave him one. Not to mention completely taken aback why a 65 year old would want one?

Did your DS want one?
Taking a stand for the reasons you mentioned seems petty to me (and I have a DD who has one for ASD reasons), injuries only happen with people mucking about, and my DD is delighted others are now using them like she does. She stands out enough. This is good.
If your MIL is generally nice I'd just grin and bear it, she did something nice for her GS who probably wanted one and didn't want to be the only one without one.
Sometimes you just have to let them have their pile of tat.
If this is an ongoing problem with MIL I'd defiantely address the behaviour but you could vome accross badly in this incidence, there must be other more reasonable complaints you can use to illustrate your point than Granny buying him the 'in' toy.