You can permanently remove the guidelines that you don't want. It's a bit of a pain, but you'll only need to do it once.
In BeerSmith, go to Options and choose to view All Style Guides.
Then: File > Open File > ...Documents/BeerSmith2 > Style1. This will open a backup styles database.
You may need to add a column to see which guidelines are associated with the styles. This is accomplished by right clicking the column bar in the window, then adding "Style Guide."
You can now delete the guidelines you don't want to see. This is a permanent change to the database, so don't delete more than you need to. Once complete, close the window and click "yes" to save. Then close BeerSmith.
Go to ...Documents/BeerSmith2 and find Style. You'll see this and more with added 1-5. These are backups. BeerSmith reads the Style file when it opens and creates backups of all databases when it closes. The Style1 backup should be the one you modified. It'll be a significantly smaller file than any of the others.
Delete Style and rename Style1 to Style. When you reopen BeerSmith, your Options will still read "All Style Guides," but your choices should be limited to only the styles you want to see.
I'm not really a fan of destructive editing, but it's the only real way to accomplish what you're asking. I'd make a backup of the Style database just in case of any future needs. It can easily be inserted.