This would’ve rubbed me the wrong way too.
If you were just trying to connect to WiFi and not on a call, that’s pretty normal once you’re allowed to use devices. Unless it was during taxi or some specific moment they told everyone to put devices away, I don’t see the big issue.
The part that makes it worse is the staring and no explanation. A simple “please wait until we’re at cruising altitude” would’ve solved it.
Some FAs are great, some are clearly having a rough morning. Still doesn’t feel good to get called out like that in front of everyone.