The 22-year-old, who has since apologised for the misdemeanour, has been released to play for Harlequins this weekend, but Johnson insisted Care would still be in contention for the Six Nations clash against France on 15 March.
"Danny's decision to do what he did was a wrong decision. He needed to keep himself in the game and not give himself the chance of being penalised and then sin-binned," said Johnson.
"It cost us three points. It was an 11-6 game that went to 14-6. We scored a late try but it could have been the winning try, possibly, but ultimately it wasn't. He understands that.
"Young players occasionally make bad decisions and some older players do as well and it's about eradicating those.
"Danny Care's played about 10 minutes of rugby in the last five weeks so he needs to play. He hasn't started a game since January so the best he can do is go out there for Harlequins."
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