The Hoops boss had cancelled the pre-match press conference ahead of the trip to Tayside, but before the game, when speaking to BBC Scotland, he claimed the club had been accused of trying to profit from administration-hit Rangers' financial worries.
"We decided not to hold a press conference this week because of all the nonsense going on elsewhere," he told BBC Scotland. "People accusing our club of trying to put people out of work at Rangers. It's in the hands of our legal team and it's probably best not to talk about it."
He added: "(We want to) get our heads down and we want to talk about football.
"A lot of media outlets will be disappointed because we won't be speaking to them. We'll do our speaking through the club.
"I'm angry but I'll deal with it in my own way."
United boss Peter Houston had not seen the Robbie Neilson incident again when he appeared at the post-match press conference.
However, he admitted disappointment in his experienced full-back whom he believes did not have to make the challenge.
"I feel it's hard enough trying to beat the champions-elect with 11 players never mind 10," he said. "I haven't seen it yet but what I would say is that Robbie is on a yellow card and it's a challenge that he makes inside Celtic's half.
"I can understand if it was around the penalty box and they were going to score. He is not a dirty player but he is an experienced enough guy, he should back off and not go into a challenge like that."
Source: PA
Source: PA