So I guess that if you're a white guy in America who lives in a $3 million dollar suburban McMansion, the way you "flex" is...to show off the tailgate on your ridiculous Totally Pointless for the Suburbs Prestige Purchase, otherwise known as your Chevy Truck.
And if you're a black guy in America, you humor your white male neighbor by letting him spend ten minutes gushing about his tailgate like a 12-year old who just got his first dirt bike.*
And if you are the neighbors of this white guy, you hate being reminded how incredibly shallow your suburban life is, but also enjoy mocking your neighbor for "flexing" about his freaking tailgate when he ought to be "flexing" about something that really matters- like the new riding mower you just got to trim the grass on your postage stamp-sized lawn, or your new $2500 grill you got because you heard the guys at the office mention that it was the model that came with 140 features, 139 of which you will never, ever actually use but WILL enjoy showing off when you can get the three people in the neighborhood who can bear your company to come over for a barbecue next summer.
And getting back to that white guy- sooner or later, he'll realize what a total black hole his life has become (having been reduced to bragging - I'm done with the whole "flexing" thing- about how his new truck comes with this expandable tailgate which made it totally worth the extra five grand he paid for a truck he absolutely doesn't need) and just blow his brains out, hopefully with a classic rare Lugar that shows good for the neighbors.
*oh, and you both wear oversized, untucked shirts to disguise the fact that neither of you has seen the inside of a gym in ten years and couldn't actually flex anything worth flexing if your life depended on it.