I think you're half right. Calculations, yes, observations, no. LeMaitre realized that Einstein's equations of general relativity led naturally to an expanding universe, but the observation of an expanding universe did not yet exist. Einstein (incorrectly) handled the problem by adding an extra term into his GR equations - LeMaitre stated that the term didn't need to be there if the universe originated from a primeval expansion. Eventual observations proved his hypothesis. But you are right - scientists shouldn't have bashed the man's idea, because what he proposed was a testable hypothesis. (Interestingly, Russian physicist Alexander Friedmann drew the same conclusions independently of Lemaitre.)
I took this to mean that he had personal observations of red shift.
"After his ordination in 1923, Lemaitre studied math and science at Cambridge University, where one of his professors, Arthur Eddington, was the director of the observatory.
For his research at Cambridge, Lemaitre reviewed the general theory of relativity. As with Einstein’s calculations ten years earlier, Lemaitre’s calculations showed that the universe had to be either shrinking or expanding. But while Einstein imagined an unknown force — a cosmological constant — which kept the world stable, Lemaitre decided that the universe was expanding. He came to this conclusion after observing the reddish glow, known as a red shift, surrounding objects outside of our galaxy." http://www.catholiceducation.org/articles/science/sc0022.
Such bashings in science tend to be short lived, particularly if the new idea is a mathematically correct extrapolation of an existing theory.
Actually, redshifts had been observed a decade earlier, but no explanation for them had been proposed.