Disagree with the title.
What one should try to avoid being, is a dick. Help people improve. Point out their weaknesses and how they can improve, but get your ducks in a row beforehand - don't be a hypocrite. He who lives in a glass house and all that....
Have empathy, and understand your surroundings, as well as reading the room with context. Be direct with people, don't waste their time, but don't be rude or crass with them. Pleases and thank you's.
If someone is falling behind at work, talk to them and understand why - don't just fire them (perhaps something outside of work that is serious is weighing them down - if that is the case tread with caution, and don't be so quick to make a decision that could cost you or your organization socially or fiscally down the road). If you must cut ties with someone, make sure you do so in a direct, honest and respectful way. If YOU were to be fired, how would you like to be treated? There's your baseline.
Don't act like an HR drone trying to use flowery language around everyone. Be respectful of everyone as well as their time, and have a baseline level of professionalism that is applied to EVERYONE regardless if they are above or below you on the org chart. Every organization I've worked in, everyone from the janitor to the CEO got a "good morning" and a "yes sir/no sir" on a daily basis. Respect in life is earned, but there's a baseline of where it should be a given. Treat people with dignity.