> One source of the story of Plato being sold into slavery is Lives and Opinions of Eminent Philosophers by Diogenes Laërtius. An English translation is available online [1] on Project Perseus. You can find the full story in Book 3 that discusses the life of Plato.
[0] https://history.stackexchange.com/a/37499
[1] http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%...
If Plato had actually been a slave, his lifelong commitment to anti-democratic political organization would've been a little different, though maybe not, considering even this experience didn't change his philosophy, to the point that's likely not worth mentioning as a significant experience, unlike Epictectus who was born into slavery.
It completely ignores very real and deadly politics of that city prior and reasons why Socrates was hated.