Also, trademark creates a legal right. Whether that creates a moral right likely depends on your take on moral philosophy.
My photo is me, by bio describes me and expressly says I'm not the musician (and gives their actual username) and yet I get mentions all the time.
That's people not understanding, not caring or not bothering but it's not really confusion about our two identities.
As this guy doesn't run a tech conference he has zero chance of defending that TM.
A guy named Joe Blogs similarly has zero chance of stopping "Joe Blogs(14)" the conference
One Rackspace would be in the industry of technology; the other in the industry of hosting conferences. The likelihood for confusion arising from the conference having technology-related subject matter is merely a factor in determining whether the conference would violate Rackspace's trademark. It's very likely that a trademark violation would be found, but it's still possible that a violation wouldn't be found.
Note also that Rackspace only trademarked "Rackspace," so "RackSpace," "Rack Space," and "Rack-Space" are separate marks a tech conference could use those without infringing upon Rackspace's trademark.
(Companies do often allow quasi-independent organizations to run quasi-associated conferences but this is usually a deliberate decision.)
Legally, technology and conferences are entirely separate industries with very different business, legal, and tax considerations. A technology company that makes software for conferences is not in the conference industry; a conference with technology subject matter is not in any of the technology industries. This may be splitting hairs, but the law is always a matter of splitting hairs.
Unless you've trademarked it, which you should probably due to prevent people who are terrible at their marketing job from absconding with something you value. A trademark application is something like $275.