Be Yourself

In every school a "top" crowd (the elite/the social elite/the trendsetters) set the pace;while the others follow they (their) lead. Let's say the top crowd decide that it (is) smart to wear bright red sweaters. Pretty soon(,) everybody is wear(ing) bright red sweater(s). There is nothing wrong with that, except the fact(多余） that in (for) some people a bright red sweater is extremely unsuitable unbecoming（不明白原来的意思.是不是“不像话"? . The situation can even become dangerous, if the top crowd decide that it is smart to drink and to driven cars at 70 miles an hour. Then (In this case,) the people who follow the leader are (now/actually) endangering their lives.
Now,changes （chances） are that you have (came) accross this a situation like this more than once in your life; chances are that one time or another you probably did something you knew to be (/that is) wrong. You may have excuse(d) yourself by saying, "Gee, the crowd does it." Well, let the crowd do it, but you yourself should not don't do it yourself. Learn to say "no".
Remember this in your heart, you are unique, just be yourself.

that in some (for) people a bright red sweater is extremely unsuitable unbecoming（不明白原来的意思.是不是“不像话"?）

Unbecoming 除了 "不像话"，也带有 "成何体统" 的意思。

不可以用来表达“荒谬”

except that some people look ridiculous wearing bright red sweaters.