it's possible to be succint, harsh, and directly to the point without swearing or being abusive. for example, off the top of my head:
"stephen, this code is riddled with basic errors and is completely unacceptable. please fix a, b, and c immediately and know that if you make mistakes like this again, your contributions will no longer be welcome."
versus:
"stephen, WHAT THE FUCK IS WRONG WITH YOU??!?! seriously, a FUCKING JUNIOR DEV would not make mistakes like this. why are you wasting my time with this FUCKING BULLSHIT? FIX IT NOW OR YOU'RE FIRED!"
imagine in both cases the person writing to you has only a professional relationship (ie, is not a friend who has the type of relationship with you where the 2nd paragraph would be an establish, half-joking form of communication)