The 67-year-old shared a photo of the late scientist, who died at the age of 76 on Wednesday.
Paying tribute to the theoretical physicist, Kirstie wrote: “You had a good go at it… thanks for your input.”
But the Star Trek II: The Wrath of Khan star sparked outrage amongst social media users, as many were left un-impressed by the comment.
One person wrote: “Very strange way to give respects to a Legend… make sure to show this tweet to your psychiatrist, hun.”(sic)
“He was a brilliant mind and he will be missed. RIP Steven Hawking. I am unsure if you are joking or serious with regards to your tweet. It seems disrespectful and quite frankly I wonder why you tweeted that? If it were a friend of yours would you’d been so abrasive?,” penned a second.
Meanwhile, a third follower asked: “This seems almost passive aggressive… is she unhappy with him? Does this have something to do with Scientology? #confused.”
A fourth hit out at the Scientologist, writing: “You’re just mad he followed actual science.”
Touching tributes poured in across the world this week, after it emerged that the English cosmologist had passed away.
Eddie Redmayne, who portrayed the Cambridge-educated scientist in the 2014 film The Theory of Everything, said the world had lost a “truly beautiful mind”.
In a statement, he stated: “We have lost a truly beautiful mind, an astonishing scientist and the funniest man I have ever had the pleasure to meet.
“My love and thoughts are with his extraordinary family.”
Stephen, who was diagnosed with a rare early-onset slow-progressing form of motor neurone disease, was father to Robert, 50, Lucy, 47, and Timothy, 38.
His death was confirmed in a touching statement written by his three children, which read: “We are deeply saddened that our beloved father passed away today.
“He was a great scientist and an extraordinary man whose work and legacy will live on for many years. His courage and persistence with his brilliance and humour inspired people across the world.
“He once said, ‘It would not be much of a universe if it wasn’t home to the people you love’. We will miss him forever.”