Aaron Carter Disses Justin Bieber [Again]: Commando, Calvin Klein Underwear Instagram Shade

Aaron Carter enjoys flaunting his chiseled abs on Instagram - but is the 28-year-old singer hotter than Justin Bieber?

Earlier this week, Carter seemingly mocked the "Sorry" crooner online - again:

Remember, 21-year-old Bieber appears in many sexy underwear ads for the renowned clothing company:    

So, was Hilary Duff's ex-beau throwing some major shade at the beloved pop superstar? Well, several Beliebers are definitely NOT amused:

joniredstone7: "Lol. @CalvinKlein won't be knocking on your hot mess door any time soon, you Bieber-obsessed c*nt." 

rick__s.c1: "Gay as f*ck." 

usawinston: "but I'm sure you wouldn't reject their sponsorship amirite?" 

But, on the other hand, Nick Carter's bro does give Bieber a run for his money in the "hot body" department!

clarkedeveau: "Would love to help you out of those pants." 

i_douglas: "@aaroncarter damn, how are you so sexy? It's unreal." 

mike_loaf: "Swing by my place and I will check in person... Lol. Great pic!!!" 

alettavdh: "@aaroncarter omg! sooo hot, sexy, gorgeous... just wow, u r beautiful my darling." 

mattypop39: "Seeing a line of hair is my weakness... Aaron I can't deal."

So, will Selena Gomez's former lover even respond? Meanwhile, rumors now suggest that Carter's "getting close" with cyber sensation, Chris Crocker. Are they really romantically involved?

Sound-off in the comments section below MstarsNews readers!