The pro and the con of coming to a forum like this and asking a question like the Op asked is the spectrum of answers you get. There are always a couple posters who think that everyone who asks such a question is a completely inept and clueless newbie, so they give them the textbook "safe" answer, even though they may or may not exactly follow their own advice. Then there are those who have tons of knowledge and experience that enables them to safely manage taking more risks than the average person and are willing to share that knowledge with those who ask. Both ends of the spectrum are the right advice for the right person, and the wrong advice for the wrong person.
Personally, I have sanded, trimmed, and re-balanced many props with no problems. I also have enough experience to examine a prop and make an educated decision as to its viability. I also have been taught enough safety habits from experienced folks that if a prop does fly apart, I'm not likely to be in its path, or allow anyone else to be.
That being said, if you really are a clueless newbie, then you'd better follow the safe advice. Don't risk your own safety or anyone else's, throw the prop away if you have any doubts about it.