Vinman-
You can disable the email notifications. That's step one. Step two is not denying "all the invites"...you simply ignore them. They will build up and never be responded to. That's all there is to it. The little spot in the right corner of the top menu tells you when you have New Notifications. If you click the link, it tells you what those notifications are. If they are Friend Requests, you simply ignore it and go about the day. You don't even have to see who they are from. Occasionally you could go through and mass-delete all of them, but I doubt it will be necessary. You could even go so far as to put in your signature, "Please do not send me friend requests as I do not use this function. Thanks". It's polite, and tells peole straight away that if they send a request and you don't respond...this is why. And nobody gets offended...
The only reason I say anything is because I have grown to respect you over the last couple years, and I really appreciate your insight and knowledge here. You're one of the "Take no B.S. Give no B.S." kind of people I appreciate on this forum, and I hate to see your participation drop off over something so trivial. It really is an easy feature to ignore, even if there isn't a coded option for it in the programming.
With that said...I have just come to realize that I have been using the Friends feature on a few different forums over the last year or so, and this is absolutely the first time I have ever encountered ANY sort of "drama" because of it. Just shows to go ya'...