http://www.sfweekly.com/2002-08-28/news/bad-vibes/
So sure, try it, but if it doesn't feel right, don't force it.
And of course some people will 'react poorly'. For most people it's the first time in their lives they've actually sat down and looked at themselves. This can be shocking.
Ignoring the problem doesn't make it go away though. That's just 'treating' the symptoms and ignoring the causes, just like we do with modern medicine.
I think you mean, "just like we do when we misuse modern medicine."
There are an amazing variety of human brains, and if you accept the results that meditation causes measurable physical changes in brain structure, you should also be open to the idea that for some brains, those changes might interact badly with other preexisting (and quite possibly inherent) brain tendencies.
People should know that if they have bad reactions, it's not necessarily a matter of 'doing it wrong', or just fighting to get over an initial challenging hump. Stopping might be the right thing for their brain health.
17% of 30 = 5.1 people. Why not just say "five out of thirty indicated ..."?
They are just another distraction, like any other thought but visual. Just let them go. The bigger a deal you make of them, the harder that will be. Acknowledge them and let them go.
As you progress in your practice you might have spacial and auditory hallucinations too. The same thing applies here. Just let them go.
Our brains constantly seek patterns in a sea of stimuli, and sometimes they create meaning out of noise. (http://en.wikipedia.org/wiki/Pareidolia)
"We are all greater artists than we realize." -Nietzsche