Here's how I read the OP's story:
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Dad: Hey, son, I bought this Benchmade balisong knife new in 1985 and now I'd like to give it to you.
Son: Wow, that sounds great, Dad, but it looks kind of beat up. How 'bout I send it to Benchmade for you to see if we can get it repaired or replaced under Benchmade's lifetime warranty first?
Dad: Sounds good, son! I sure raised you right!
(Son sends knife to Benchmade)
Benchmade CS: Sir, this knife is damaged and under the lifetime warranty, but we can't repair it and are unwilling to replace it. How about we offer you $75 off MSRP for any knife on our website which means we actually make money off this deal instead of honoring your warranty. If you don't like that deal, how about we give you 30% off MSRP for any knife on our site, which will be probably higher than MAP price anyway so we will be making even more money off that deal.
Son: Excuse me, I just want the knife repaired or replaced per your warranty.
Benchmade CS: Too bad.
Son: I've had a negative experience and I'm going to let my online buddies know about it.
Benchmade CS: Go pound sand.
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I certainly didn't read the statement about posting to BF as a threat or blackmail. Blackmail would be 'give me a new knife or else I'll tell everyone'. Deciding to tell everyone and then letting Benchmade know that you plan to do just that isn't blackmail at all; on the contrary, it's letting them know that you believe they are in the wrong and you're going to let others know about it as well.
I suppose everyone here just trusts benchmade to always do what's right. I like Benchmade as a company, I own lots of Benchmades. But they aren't infallible. If they make a mistake, it's up to the consumer to keep them honest. Free pocket clips are not the same thing as honoring a lifetime warranty.
It certainly isn't the OP's fault that Benchmade can't repair the knife, nor is it his fault that Benchmade doesn't sell $50 or $100 balisongs anymore. They should have offered him a free replacement of equal (or slightly greater) value. Not a $400 balisong, but maybe a Griptilian or something.