I have no issue with characters swearing, but they should be professional enough not to do it on the job unless there are no superiors around and you're really comfortable with everyone in your company.
And let it be noted that the one instance we've seen had Tilly looking slightly embarrassed at her lapse, and her supervisor letting it slide because the three of them were having a moment. It's not as though people on the bridge are swearing all over the place every time they go to Red Alert.
It's one thing to have "professional" standards. It's another thing to expect our characters to be perfectly cool and professional at all times. STAR TREK is not about perfect people who always behave impeccably. It's about flesh-and-blood human beings who react emotionally sometimes.
(Pretty sure that if they filmed "The Corbomite Maneuver" or "Balance of Terror" today, there'd be some harsh language amidst the more emotional outbursts.)