Undermining democracy - har har har
A couple of Facebook ads are not what is undermining democracy.
Undermining democracy is things like political and business elites getting away with behaviours that would see commoners put away for long periods of time - whether that's molesting staff or endangering secret information.
It's things like supra-national organisations ignoring democratic results because they're inconvenient to their oh-so-important projects. Demanding the elections/referenda get run again and again until the "right" result is generated.
It's journalists writings on how terrible it is that democracy means that building (for example) high-speed train networks are just too hard because peoples opinions have to be taken into account instead of being overruled like they do in the paradise that is China.
It's hordes of "you can't say that" twitter-twatters trying to prevent dissenting opinions from being discussed.
Cheesy political ads are not the cause of this, they're a symptom.