Some people genuinely do not pay attention to current affairs until ten seconds before election day, and then get flustered by the competing narratives. That's an option too.
First, Biden isn't talking about banning all guns, he wants to regulate assault rifles and institute mandated background checks to stop children from being shot in their own neighborhoods every day.
Then, his administration includes the first black vice president, 25 appointed black judges, wrote that executive order about protecting minority voting rights since they're targeted so often.
On the other side, dumps will say anything to get you to vote for him, and goes back on his promises anytime it's personally inconvenient, so you can't trust anything he says on guns or racial Justice.
Trump has apparently has given zero thought to racial Justice, which shouldn't be surprising to anyone.
A hardcore second amendment voter will usually resist any and all measures that restrict firearm possession, often on the basis of slippery slope arguments. Since the basis is rooted in a classic logical fallacy, they can be very difficult to persuade.
You're right though, Biden has been fairly moderate on gun control. So was Obama though, and you remember how they reacted to him?
Reagan enacted the assault weapon bans when he was governor of CA in direct reaction to the growing popular power of the Black Panthers. So yeah, even people who actively work against racial justice know exactly what the score is.