They will tell you that Hollywood stars shouldn't be involved in politics because they're rich and has no experience in government, then say they love Trump because he's rich and never worked in government.
At the least it counters the Sleepy Joe rhetoric aimed at swing voters. It won't convince the true believers (because they don't believe in anything but destroying the left) but it might slightly change the swing voters' impression of Biden (and of Trump) if this line of attack is neutralised.