Well it's at least more sensible than kale, turmeric or activated almonds. Being overweight may be another trigger (cause is much trickier) and exercise may help avoid that.
Simple answers are always popular and often really hard to substantiate. If it were that simple, cancer would be very rare. As you say the intentions are not necessarily bad, just wanting to scare off the cancer bogeyman with a quick fix. Exercising the hand muscles to donate some money to complex cancer research might be an option to suggest.