Worlds Greatest Graffiti Remover Wipes. I picked up samples at the NJ event. They saved me twice. We got some stain on brand new pavers, 2 quarter size stains. It came right out. Pavers are less forgiving than vinyl.
Vinyl is inexpensive, just swap out the ruined panels.
Presuming the vinyl on your home is still available, Zach nailed it. Goof Off will work as well, BUT it will likely change the sheen of the vinyl for a few years. Just swap it out. Problem solved. Of course Ed knows his stuff as always.
This is exactly why we don't stain decks as part of our service offering. The margins and the liability just don't fit our business model.
If its fresh stain try lacquer thinner or HD sell Graffiti spray. Put it on a rag and rub lightly. Don't use Goof Off! Also you put blue siding on your home, What no green?