From a server admin's perspective...(and NO, we don't have that rule on our server)
I prefer to see servers have this rule for one very simple reason...if you get pwned too much and you're in the base and you can't even spawn, you leave. Plain and simple. I've seen it on our servers and on other servers. It's one thing to get wasted because you aren't so good...it's another thing entirely to be in a server where you can't even move, after your spawn, before you die.
Make no mistake, most times (if not ALL times), the team getting spawn raped EARNED the beating. The only qualification here is when servers to do not have AB on and the teams are dreadfully uneven. However, if you don't give people a chance to move, they'll leave (or are stupid not to...). Now the server loses. Period. Empty servers are a bad thing. Yes, we pay for the server to be available at our convenience. However, full servers are generally the fun ones.
I can accept if your penis is SO friggin small that spawn killing is about the only way to feel the endorphin rush...I was once like you, then I got Enzyte, the once a day pill for natural male enhancement, and I got over it.
Oh, and kills don't diminish with this rule per se...the folks in the base don't generally sit there (OK, some do, but ??!), so you simply wait at the door and knife 'em when they come out.