Collum took charge of the fixture for the first time at the weekend and sparked controversy with some of his decisions.
Celtic boss Neil Lennon was unhappy after Rangers were awarded a dubious penalty and also claimed Lee McCulloch should have seen red, as the Hoops lost 3-1.
But Webster - who did not make the squad for the visit to Celtic Park - had sympathy for the referee, who apparently received threats in the wake of Sunday's match.
He said: "A lot of the time, there is a lot of emphasis placed on the referee.
"Watching the game on television on Sunday, there were a lot of stats coming up about the referee and stuff.
"When you start highlighting the referee in that manner, it maybe puts unnecessary pressure on them.
"People say a referee has had a good game when they are quiet and unassuming.
"It's a difficult one. It's a high-pressure situation, especially in Old Firm games, to be able to handle it and I thought the ref did well.
"It's a difficult job and not one that I would relish.
"Generally, you are never going to win as a referee. It's a difficult job to do and they do it to the best of their ability."
Webster has put his injury troubles behind him but has so far been unable to force his way into boss Walter Smith's plans.
He has made just one appearance so far this season, in the 7-2 win over Dunfermline in the Co-operative Insurance Cup, and is set to be involved again in Wednesday's quarter-final at Kilmarnock.
He said: "I'm just looking for an opportunity, the same as everybody else.
"When it comes, hopefully I'll take it. The team has done exceptionally well so for anybody to get in at the minute is difficult.
"I just need to bide my time and work hard in training. We play practice matches and I'll work hard in those and wait for an opportunity to come around.
"With the size of the squad that we have now, I would think there is more of an opportunity to get a game.
"From that point of view, the manager is going to have to utilise the full squad and hopefully, being part of that, I'll get a game."
Despite such a compact squad, Webster has no fears about Rangers' ability to cope as they attempt to juggle their domestic commitments with an impressive run so far in the Champions League.
The defender said: "There is a lot of quality within the side and a lot of players who can play in numerous positions.
"Of course it's going to be physically demanding on the players but I think that's something they relish.
"You want to do as well as you possibly can in every competition you go into. The boys relish the challenge and it's not something they've not been through before."