The other senator is a lost cause.
Maybe not. They might be a "lost cause" on firearms, but unless they're one of the co-sponsors of this reanimated zombie bill they may be persuaded by citing the state legislation, federal background AND Chief LEO approval requirement, 42 other states with legal suppressors, and the inevitability of this legislation not passing or possibly even not clearing committee hurdles because 80% of the states support suppressor ownership and use. Tell them you understand the need for politicians to make these sort of dead on arrival legislation, but it is never beneficial to side against the overwhelming majority on something already heavily regulated at the federal level.
Can't hurt to take that approach.