They aren't doing anything funny, nor are they asking you for permission to do anything funny.
They scan your ports. To the unobservant, that can look like they are trying to crack your systems. What is wrong with recognizing their IP (adding it to your "whitelist"), and knowing that it probably isn't something worth investigating.
Also, did their webpage get hacked and that ip changed?
Will someone with access to their machines network succumb to maliciously using or selling access to this widely whitelisted ip?
Seven years from now will that ip still be theirs?
And we're not talking about a literal software-implemented whitelist, just a "it probably isn't worth investigating or sending complaints" whitelist. That makes the seven-years point less important.
What's up with this belief that anybody you haven't heard of is a member of some shadowy organization? I'm a well known security researcher, I give several presentations a year at cybersec conferences, and my blog gets regularly link to from news.ycombinator.com.
Also, the post above excludes the first part of that: "We are happy to add your IP addresses to our blacklist so we won't ever scan you again".
I understand frustration that you can't convince everyone that you are a good guy. All good guys these days have that problem. Even the good folks at the NSA ( you aren't one of them, are you? )
I'm not white-listing anyone I don't know.
> so you can search your logs for it to make sure they aren't being evil.
This argument doesn't apply if the probe and the attack come from different IPs