Qualifying Your Statements

Root the statement in your own experience
"Every teacher I've had at PCC has been terrible." (then go on to give examples of their terrible teaching, and perhaps speculate on the causes of the trend; if you can do both, you've proven your point and achieved your desired aim–to trash PCC.

Replace "is" with "may" or "might"
"The end of the world may be near."

Use a "frequency" qualifier
"Most of the teachers at PCC are terrible." (and most teachers would probably agree with you– as long as they're not included) Other such words: "for the most part," "on the whole," "generally," "usually," "many," "almost never," "almost" always, "a number," "an alarming number," "an impressive number," "a disappointing number," etc.

Use a "speculative" qualifier
"It may be that the teachers at PCC are terrible." "It seems that the teachers at PCC are terrible." "The teachers at PCC are perhaps terrible." "Probably" is a little stronger. Others: "seemingly," "possibly," "apparently," "presumably," "allegedly"

Add a qualifying phrase or subordinate clause to your statement
"Although a few exceptions do exist (e.g., Michael Dembrow), the teachers at PCC are on the whole a miserable bunch." "The teachers at PCC are terrible, with only a few exceptions."