They're trying to make the whole movement look dumb by proxy, or that anyone who joined the movement is dumb because they're following a dumb guy. The public PR angle is that only a dumb stupid babbling person would deny the goodness that Amazon does for its employees and try to organize a walkout.
I think it's interesting the contrast with the SVP who said he let his emotions got the better of him. If the union guy says something not-smart, he's dumb and the whole movement is dumb. If the SVP says something not-smart, he was just trying to protect the workers.
Agreed with GP that the other parts of the memo about obtaining and distributing masks don’t sound so bad at all, especially if they actually translate it into safer environments at warehouses and surrounding communities.
In general, I wish companies who want to avoid unions just treated their workers well enough that they don’t want to unionize — seems like the most straight up way to “fight” unions. It’s akin to simply improving your product to get more users instead of employing dark patterns or grey hat SEO.