Preppers tend to be a little bit on the edge anyway, IMO. A lot of them know just enough to boost their confidence enough to make themselves look foolish. There is no EMP associated with a CME however there is indeed the possibility of electronics being affected by them. This happens either in outer space where electronics are not protected by Earths magnetic field, or to power grids here on Earth. Basically, a generator creates electricity by rotating a wire coil within a magnetic field. During a CME there is a HUGE magnetic field as well as highly electrically charged particles that sweep past Earth and all it’s power lines. Crazy voltages can be induced into the power grid causing failures. In 1989 the province of Quebec had a major blackout lasting 9-10 hours caused by this. In 1994 Canada lost two comm satellites, Anik-E1 and E2. I remember this event very well, as I was working in the engineering dept. of a radio broadcast network here in Nova Scotia. I got called early one morning because we had no satellite news or programming feeds. I found the satellite receiver lit up red and the UNLOCK light was on indicating no signal. I called Toronto and was told Telesat Canada lost two birds. Eventually they were located but had drifted out of their orbital slots. One was recoverable but had a shorter life due to the use of fuel to keep it in place. Usually this is done using three gyros. The gyros were fried as the CME swept past us. It never even occurred to me to protect any electronics, actually. Simply no need to here on Earth. Power grids trip before nasties get into your home anyway when this stuff happens.
Loss of Anik-E1 and E2 January 1994