Whites who become eligible to vote in the next GE are 12 now. They were 2 when the Brexit vote happened and 5 when we left the EU. They don't care about the EU, they have no idea what it was like to live in the EU or things like free movement or Erasmus.

Instead, they grew up in a massively left wing environment that promotes niggers and pakis, vilifies white people and actively discriminates against them. They will have no appetite for Labour or any left wing nonsense. White British pupils are still 62% of the population. Add to this the portion of non-white youths who will grow up under Labour internet censorship and feminist/gay dogmas.

This is just Labour being completely out of touch as usual and thinking giving young people this right will immediately make them the preferred party with that cohort.
It's an age group that doesn't work or pay bills and will vote entirely based on cultural factors and the type of environment they grew up in. It will be the most rebellious voting group out there because they aren't thinking about taxes, unemployment or cost of living, it will just be a chance for them to give their teachers and the establishment the finger. Who do you think they will vote for?