I don't say this in a rude way and I respect your ambition, and you might be someone with the capability to deadlift 600 pounds with the right decisions and dedication. However, your belief in yourself has nothing to do with men who aren't capable.
You happen to work out in a gym where there are a few men who can deadlift 600 pounds. I currently work out in a gym in which I'd say the vast majority of men are incapable of such a feat, regardless of dedication and belief. That would change if I renewed my membership at Bev Francis's Powerhouse where I still go on occasion and where I was a member when I prepped for my show, specifically because I wanted to workout around men who are better than me.
While at that gym, I could spin something similar to what you said, but with a bodybuilding slant. I could say there are dozens of IFBB pros at my gym, male and female, some of whom are regular guys, implying that with enough dedication and right decisions and actions, any average yokel can be an IFBB pro! (Well, admittedly the chances are higher in this day and age as compared to the 90's when it was near statistically impossible to do so, but people can catch my drift.)
I agree that one shouldn't bog oneself down with such self-defeatism while trying to accomplish something; hence why I had no patience to listen to talks of FFMI, fake-natty status, and so on, when I was prepping. Like I said, I was ecstatic about what I achieved, but I will not be stepping onstage with Phil Heath.
When we say average men, I'd like to pinpoint what we are considering average. I say average is someone with genetics of five on a scale of ten considering I don't know how else to put the genetics issue into perspective. Many men have genetics below this figure I go by. I believe men with genes below five for strength or muscular gains as incapable of looking like a bodybuilder, and certainly being unable to deadlift 600 or even bench press 300. Which is why I can't agree that ANYONE can accomplish a 600 pound deadlift. Perhaps if someone said, "most men with decent genes can deadlift 600," I'd be right on board. But I think to say ANY healthy man (free of disease or other abnormalities and can complete activities of daily living) is totally unrealistic.
And again, that's your gym. If you went to a Life Time Fitness or Bally's around here, you wouldn't be able to say, "My gym has multiple 600+ plus pullers."