1) Easy - there are algorithms developed by SCIENTISTS to ensure that districting gives a fair result which does not favor either party - the end result is determined one a genuine one-man-one-vote basis. This is not a job for politicians - there are no philosophical questions about this, it's a job for scientists - which they have ALREADY DONE. In fact, in the precursors to this supreme court case some such scientists testified in the earlier trials - and showed how a fair electoral map would look. It's a solved problem.

2) The right for everybody's vote to count equally. If you use demographics to redistrict in the way republicans do - you allow people who are likely to support you to have their votes count for (a lot) more than everybody else's votes. You're not seriously saying that "possibly persuadable" means "where the districts are drawn is unimportant" are you ?That's INSANE.