Somehow related. Post-Brexit, many young liberal europeans I know suggested stripping older UK nationals of their voting rights. Just like that, you'd be amazed how far people can go with this.
Anyway, both opposing points of view, while having some merit, are simplifications. Both old and young people should be allowed to vote, and you'll have to find a sensible cut-off at what age to start.
Of course, then it depends who actually turns out to vote, and I believe the younger folks could have been a bit more active on the day of the brexit referendum. (Of course there were also other reasons why "leave" won, including blatant misdirection and cheating by the leave campaign.)
Talking about disenfranchisement - what baffles me the most though is that UK expats living in Europe, who had a disproportionately high stake in the outcome of the referendum, were apparently not allowed to participate.