By my way of thinking somebody misinterpreted advice as a dictate. I’m certainly no religious scholar but I find it quite funny that people get so worked up over what they eat for reasons other than what they don’t think tastes good or does not agree with them.
I’m happy to let anyone impose upon themselves whatever restrictions on diet they like, but getting back to the subject of this thread who told these people anything at McDonalds was good for them.
Further, if it is so important to them, why did they let down their god by only taking McDonald’s word over an issue they considered so important?
Any food establishment should not change its menu in a big way just to serve a specific population - on the other hand, business is business.
I do not think a Jew would take MacDonald's word that the food is Kosher. Muslims might, not sure.
An observant Jew has to see proof (a diploma) on the premises that the place is under “supervision” by an external “Mashgiach” or overseer. Then again, there are various levels of Kosher strictness.
A person should seek out what is good/healthy for them but certainly not dictate to others what they need to do.
“Getting worked up” as you call it is right on the money but so many faiths take things to the extreme.