Wanderers opened the scoring in the second half through Chris Eagles, but Boro quickly replied as Kieron Dyer's headed effort flew past Adam Bogdan.
Jonathan Woodgate was sent off after giving away the penalty that Sordell netted to seal Bolton's eighth straight home win, to the delight of Freedman, whose side returned to sixth place with just two games remaining.
"It was a very good team performance," said Freedman. "You've got to remember that we've played three very intense games in a week, so to hang on and dig in is what's getting us in the top six.
"What you've got is a group of players who have got a spirit you can't deny. No team I believe in the top six have got that right now. That commitment is getting us results.
"We had that setback in midweek but every time we lose a game or draw a game, we bounce back and that's what we do on the pitch as well.
"If we give the ball away we quickly get it back and this is what the team is all about."
Speaking about the play-off challenge, Freedman added: "The play-offs are in our own hands now, but it's still going to be difficult with us having to play Cardiff and then Blackpool.
"However it's a great thing to have at this stage of the season and we wouldn't want to have it any other way."