Emotions are unavoidable but being overly emotional is an issue. A person who is healthy and in control of themselves can regulate their emotions. Angry outbursts, letting something that didn’t go your way ruin your mood for long periods, the inability to control jealousy or envy, want for revenge - all very problematic and unhealthy.

Also, anyone who is reflexively emotional can be controlled. You either control your emotions or they control you. And when malicious people realize this they can also easily control the emotional ones.