傷ましい(←かわしそうな)先生は、
自分(=先生)に近づこうとする人間(←主人公)に、「
私(=先生)は、あなたが私に近づくほどの価値のないもの(←者=人間)だから
(私に近づくのは)止せ」という警告を与えたのである.
The pitiful Sensei gave warning to those who were trying to come closer to him;
"I'm not as valuable a person as you come closer to me."
The pitiful Sensei was just indicating a signal, "you should not become my friend because I'
m not worthwhile to be your friend," to those who tried to be his friend.
The pitiful Sensei made gestures indicating:
1. He thought of himself as a valueless person.
2. He thought that I
should keep my distance from him because he was valueless.
There are a lot of ways to make "
correct" translations.
近づく literally means "come closer" which actually means "become intimate," "become friends," or "become a closer friend than just an acquaintance."
It's a figurative expression from a certain viewpoint.
And a figurative expression may not make sense in another language/culture.
So, you should think about the translation which makes sense in that language/culture.
Therefore, you cannot get only one "correct" translation, which is absolutely correct.
Persuing one absolutely correct translation is merely an illusion, IMHO.

Hope this helps!
Thank you.