I'm definitely pro science but we can't ignore that sometimes simply "it's science" is used to propogandize. It's like the way "this bill is to protect children" is used (this one is used a lot for more control over technology, backdoors, etc). It's impossible to argue against that without being ridiculed and shamed, even if the method or desired result doesn't make sense or is antithetical to the claim.
Science, used vaguely, can be misrepresented, used to create logical fallicies, etc. We equivocate just the word science with truth and reality and that can be taken advantage of.
So science isn't leftist propaganda, but science and the claim of science can be used as propaganda, just like anything else.