This is a primary. Everyone's life is under examination. It is particularly important this time given we have an megalomaniacal oaf and racist in the WH. Even Kamala will get her life turned upside down. Biden is not a racist and did very many great things in his life. But still, this is one aspect for which he has demonstrated no reflective retrospective. It asks for an answer.
I am sure that an examination of Sanders will also find him wanting in terms of his political behavior.
People have to understand politicians are a creature of their times and this informs how they behave so anyone who was active in the 90s will manifest behaviors that will be seen as unacceptable in 2019.
Even the Black Caucus advocated a "tough on criminals" advocacy in the 80s and early 90s because in that era many black neighborhoods were killing fields. 2,200 were killed in NYC and even middle class areas in SE Queens became dangerous. They blamed crack dealers for this so urged punitive measures to be taken. In hindsight this had negative impacts as the police became an occupying force in many black neighborhoods and the abuse and excessive arrests destroyed many lives. So many pretend as if they weren't complicit in what happened, but their voting records will show otherwise.
Obama deported 410k people in 2012. Trump deported 250k last year. When Obama sent ICE to deport people they didn't care whose kid was abandoned at daycare while their mother was being hustled over the border to Tijuana. Quite a few became orphans when Obama deported their parents, and who knows how some of these kids ended up.
When Haitians attempted asylum in the last years of Obama, using the same reasons that Central Americans now use, Obama told them "no" and many were forced to start new lives in northern Mexico. And in fact some of the abuse on the southern border is a heightening of tactics that began under Bush and continued under Obama.
Many attempting to enter the USA illegally met their deaths in the deserts as US presidents deliberate tried to discourage this by forcing people into harsh environments. While the recent deaths in the Rio Grande were tragic so were many more in the deserts of Arizona where only skeletons remain and where much of the flesh was consumed by the coyotes.
Open bigotry by Trump has caused people to condemn acts that they ignored under Obama. When the Hispanic caucus called Obama "Deporter in Chief" few cared.