One bad apple can spoil the whole bunch and/or barrel!
idiomation.wordpress.com/2013/03/27/one-bad-apple-spoils-the-whole-barrel/
wonderopolis.org/wonder/can-one-bad-apple-spoil-the-bunch/
I firmly believe that we are products of our environment. If you hang around a bad apple, you can become a bad apple yourself. The say a positive and a negative becomes a negative. The law of science, which has proved true in my own life. We lived next door to three brothers who swore up a storm. They made up new swear words or they said words that made them sound like swear words. When I came into recovery, this little Christian girl who went to church and Sunday School, had a mouth like a long shore man. That is why my sponsor and spiritual adviser for NA said to clean up my body, mind and spirit and that means clean up your mouth.