People make a lot of assumptions in day-to-day life — from assuming no one is going to eat that last Pop Tart that's been there for a week to not going down the dark alley you assume is dangerous. Assumptions can be both good and bad. In some situations, they can even be lifesavers! But then, there are the quick, factless assumptions that make not only you, but also those who associate with you, look like a*ses.
Assuming anything about anyone without facts is like writing a research paper without researching. Coming to quick conclusions only causes problems. I know Bob has been distant, even though you offered him waffles, but maybe he has something going on. It may not be you, the tough math test that day or anything remotely similar. The best way to know what's going on is to ask what's going on.
The rule about avoiding assumptions extends beyond being just about people. Jumping to conclusions about events, theories, places and other concepts can make you the butt of the joke too. Just because a school is located in the South doesn't mean it's worse. And that poetry unit in your literature class might actually be interesting. Why shorten your experiences because you think things could only be a certain way? That doesn't make sense. There's nothing fun about making assumptions.
More importantly and sadly more prevalent is racial profiling. Some say everyone is a little racist and that it's naive to think otherwise, but that's not true. Change your mindset and never discriminate, period. Generalizations are probably the most common kind of assumption people make, but everyone who makes them are ignorant.
There are times when it is okay to assume. Like I said, sometimes, assumptions can be lifesavers. That dark alley probably is dangerous. Why is it okay to assume that? Because past experiences and learning from other people's experiences taught you that. If someone hasn't eaten that Pop Tart in the two weeks, it's been in the cupboard and is going bad, so it's safe to say no one wants it. It never hurts to ask, but you generally don't save food to eat when it goes stale. Common sense will tell you that. The only way to make a good assumption is to use facts and previous experiences to come to a logical conclusion.
Anyone can make quick assumptions, so don't let yourself be that guy. If "Tucker Dale vs. Evil" has taught us anything, it's that things are not always as they seem. Let's save ourselves the embarrassment and gain information before we make conclusions. Not to sound like an a*s, but when you verbalize quick assumptions, people hear a "hee-haw" when you speak.