Armitage, 28, was suspended from the England Saxons squad for the current international campaign after an alleged assault in a nightclub which followed the Saxons' victory over the Irish Wolfhounds in Exeter last Saturday.
The full-back was available for London Irish's final LV= Cup group game with defending champions Gloucester on Saturday, which the Exiles won 23-15 thanks to a Brian Blaney try and six Tom Homer penalties.
But head coach Booth decided to keep Armitage, who has been banned four times for various reasons during 2011, out of the spotlight this week.
He said: "He was available. There has been a lot of hype around last weekend and I thought I ought to support Delon and not put him in an unnecessary position.
"We had the opportunity to do that and I decided to do that because he's innocent until proven guilty."
Quizzed on whether the player will be available for the Irish squad that faces Quins next week, Booth said: "I would have thought so."
Former England full-back Mike Tindall played out of position at fly-half instead of his normal centre and took over the emergency kicking duties which saw him land a penalty and convert one of young wing Ian Clark's two tries on his starting debut for Gloucester.
Booth said: "There was a missed touch (kick) or whatever but normal number 10s do that. I probably thought what a well-rounded footballer Mike Tindall is, to step in there and make it not glaringly obvious that he was not an out-and-out 10."
As for the match, Booth said: "It became a bit of a stop-start. They were not blessed with some of their selections and neither were we and, ultimately, it became a bit scrappy.
"But I think we came though a good character test there, which is important. The effort was good and when we were on top, our defence was good.
"We put them under pressure at line-out, in particular, which is vital because you don't have to defend lots of phases if you can turn it over at source.
"We dictated the first 30 minutes and the signs were very encouraging."
Gloucester had a slight chance of qualifying for the cup semi-finals - and continuing their defence of the trophy won when beating Newcastle in 2011 - had results gone their way and they won the match against Irish with a try bonus point.
Head coach Bryan Redpath said: "We had opportunities in the second half to win that game. We had lots of endeavour but not too much clear-cut decision-making.
"You have players out of position and it shows how difficult it is."
As for Tindall, he said: "I thought the first half was poor. We never kicked and there were hardly any set-pieces in the opposition's half. At 10, you have to be on your game.
"We knew it was going to be tough for Mike and I didn't want to put our young lad on the bench on there as he played on Wednesday."
Redpath also praised Clark, who, along with his two tries, took some good high ball and was excellent all around the park.
"Clarky did nothing wrong today. He worked hard and did everything that was asked of him," he said. "It was good to see a young boy go out there and do well against two good wingers. He held himself pretty high in the rankings today and put some senior players to shame.
"He is still a young man and today is not a performance where we say he should be challenging Charlie (Sharples), Jonny (May) and James (Simpson-Daniel). He has come into the environment and it was great to see him finish off two tries. I'm chuffed for him."
But, ultimately, Gloucester will not be back in the final, and Redpath admitted: "I'm gutted. We could have scored four tries in that second half and come away with something more. It was not a great game and it was there for us to take."
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