When it was the last time we had an actual issue where 16yo voting had direct measurable negative impact on something in real life? I think it's as other said, we have to draw a line, and I think it's reasonable to debate this because maybe each nation prepares their kids differently so one nations 16yo isn't another, this way there isn't a universal rule. But arguing that you have to discuss ALL the other civil liberties before discussing 16yo voting rights is absurd because there is no connection between drinking and voting and all else.
I don't think children should have a say in the matter, they lack the critical thinking skills that adults do, which is why we limit their freedoms.
Granted, most adults also lack deep critical thinking skills but they have more capable brains than children.
Further, children are easier to manipulate than adults, which is very dangerous when it comes to something as critical as voting.