Not sure I'm seeing the problem the same way as others here :-(
It's certainly not (imo) rigging an election, that's done by fiddling with ballots, prevent certain groups from voting, or directly threatening groups to vote a specific way 'or else'
This is targeted advertising, finding a group of people who are likely to be susceptible to a certain message and then giving them that message.
This method is available to every political party and leaning, so all can use it to deliver their message to the groups they think will appreciate it most.
The article infers that it's a cheap way to get a message across, so in fact you could argue that it levels the playing field, it's not just the player with the most advertising pounds that wins any more.
Whatever your personal feelings on both the Trump and Brexit result, surely the smaller parties having access to spread their message as readily as a larger well funded party is a good thing?