What is your take on this?

I am still disturbed by what our teacher said during class. I just want to know what your take on this is.

Verbatim:
"Dont associate yourself with depressed people, because they are people who view the world negatively. They spread negativity. If you associate yourself with them, they will one way or another convince you to also view the world negatively and you yourself will become negative."
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I am a uni student. Ive met several people who ARE depressed and people who WERE depressed. I myself was diagnosed with depression.

I went through several stages back when I was depressed. For one, I was very sensitive to my problems. I was constantly feeling pressured by something or anything. I could not control nor suppress it and it made me really anxious. Second, doing things feels like a burden. I dont know how to describe it but I felt heavy and I was in pain (not physically). I easily get tired and the things I usually do no longer makes me happy. Third, I became numb. I didnt feel sad nor happy. Heck I didnt even feel anything that I almost failed three subjects. Everything was passive to me during that time. If given a choice I would rather just lay in bed and think about nothing. Fourth, I became suicidal and was inflicting self harm. Crying to express the heaviness and emptiness I felt no longer satiated me. I just wanted to disappear.

As much as all these "stages" I went through sound negative, I , as far as I know, did not spread negativity. Heck I was even trying not to show my depression. How does depression or a depressed person look like, you ask. We look normal. We look like the same joyous person as we were before. You can still see me laugh or smile. But personally, if im not forcing myself, I probably would just have a poker face. Physically present but mentally absent. Like I mentioned, i didnt feel anything. I was numb and everything was passive to me. (Do note that I am only speaking from my experiences and therefore will not be applicable to everyone)

Enough about me lel. So what our teacher basically said was to avoid reaching out to depressed people. I would like to make a point that the people surrounding me aka friends were a great help. I never shared to them what I was feeling or "how I was viewing the world negatively". They just know that I was depressed. They helped me pull myself together and they made sure that I never felt alone. Looking back then, cliche as it sounds, I am really grateful for them. Because without them, I dont even know where I would be now. (My family doesnt know. I didn't open up to them bc they believe that depression is not real)