From other threads I will repeat my same response... It's not LAW but many agree and I hope I can convince you as well; Never you use silicone to bed deck hardware, ever! There are only a select few places on a boat where silicone is appropriate like DOW 795 for non-opening port lights, certain gasket applications in the engine room, and a few plumbing/head uses. That's pretty much it... if you are sealing anything on deck with silicone, anything below the water line or above the water line exposed to the elements/UV you are pretty much asking for it (it could cost you big time later).
If you have to re-bed something and you discover it was previously sealed with silicone you must manually scrape away as much as possible. Sand paper is only effective once 99% of it is gone, and even still it can gum up the san paper. Silicone residue is almost impossible to fully remove, you literally must grind away some of the surface laminate. There are no common chemicals that I have come across that 'dissolve' and clean up silicone residue. DOW chemical has one but it is only available to industrial customers and from the MSDS it sound like pretty nasty stuff. New resin (epoxy or polyester/vinyl ester) will NOT stick to a repair where silicone residue has contaminated the surface, as I mentioned you have to grind it away.
In the case of the aforementioned stanchion that had silicone... Since a laminate repair isn't needed you don't have grind away anything, just do a good job of scraping away the silicone remnants. Butyl tape is the best sealant to use because it will still 'stick' even if the surface has silicone residue. Other sealants like 3M 4200, Sika Flex, or Life-Caulk would normally be ok to bed deck hardware, but they won't be effective where silicone residue is present.