These kind of "x-ist" statements are fine for things that are overtly x-ist. The problems happen when things are more murky; for example when you start exploring the reasons why there are few women running Fortune-500 companies. If you start shutting down things with "it's x-ist!" then you may never find out the reasons (and by extension, how to do something about them!)
"It's x-ist" is an assertion, as well as an accusations, and not an argument. It's usually much better replaced with "I think this will be bad for group x, because reason y". It has the same effect, and is actually constructive.
Lots of people have studied the question of why women aren’t running Fortune 500 companies, and unsurprisingly the answers have a lot to do with sexism.
The average age of a Fortune 500 CEI is 58. Talk to any female executive of that age and they’ll have many examples of opportunities they missed out on because of their gender.
My mum was told explicitly that she wouldn’t have got the job she was in if they had known she had a baby at home, because it was a “high-pressure job”. They offered to reassign her, she refused, and she didn’t tell her colleagues about her husband or kids for another year, for fear of having similar opportunities denied.
"It's x-ist" is an assertion, as well as an accusations, and not an argument. It's usually much better replaced with "I think this will be bad for group x, because reason y". It has the same effect, and is actually constructive.