Both the Senate and House majorities oppose a weapons ban. And in an election year, Biden is most likely wary of a ban backfiring at the polls.
He tried to pull that off once and the Republicans (as well as some members of his own party) publicly carpeted him.
1980 Elections
1984 Elections? A whitewash
Both extreme landslides.
Let's not pretend Biden's speaking from the same position of strength as Reagan et al.
Sure, he could certainly do more to stand up to Bibi. One wonders also how much his age is telling on him. He's been unduly cautious with making these strong decisions. Certainly he's made a hash of appropriately calling Russia's bluff.