The 17-year-old Macheda, a product of Serie A side Lazio's youth system, scored in stoppage time on Sunday to give the Premier League leaders a crucial 3-2 win over Aston Villa.
"It's unthinkable that a lad of 15 can be bought as if it was a cattle market," Lotito told Italy's Sky television.
"Normally these boys are not from wealthy families and they look for alternatives in foreign countries for economic reasons."
Born in Rome, Macheda joined United in 2007 and in August became the latest in a string of non-English youngsters to sign professional forms with a Premier League club.
FIFA wants to protect under-18 players and keep them with their local clubs but employment law complicates the situation.
"We knew that he was a great player, we did everything to keep him. We can not allow ourselves to behave in a way which I feel is immoral."
Lotito added that his mid-table side would be packed off on a training camp and may have wages held back after losing 2-0 at Siena on Sunday in the latest in a series of poor displays.
UNITED FANS! Check FourFourTwo.com’s ever-expandinginterviewsarchive for more stuff to read:
Web Exclusives Wayne Rooney, Peter Schmeichel, Carlos Tevez
Q&A Wayne Rooney, Cristiano Ronaldo, Ruud Van Nistlerooy
One on One David Beckham, George Best
Ask A Silly Question Bryan Robson
Boy's A Bit Special Danny Simpson
Perfect XI Garth Crooks, Bryan Robson, Sir Bobby Charlton, Eric Cantona
What Happened Next? David May, Norman Whiteside
Sing When You’re Winning Dominic Monaghan, Ian Brown
And Another Thing Being a Big Four fan
Plus! Rate United players (and others) on Talentspotter
Get the best features, fun and footballing frolics straight to your inbox every week.
Thank you for signing up to Four Four Two. You will receive a verification email shortly.
There was a problem. Please refresh the page and try again.