(Edit: This can't be said to apply to "anyone on the left," but does apply to a vocal subsection.) Literally anything having to do with race relations or COVID mitigation. If you think it's possible SARS-CoV-2 is a lab leak, you're a conspiracy theorist; if you think "it's okay to be white," you're a racist.
There are a lot of sources of anti-science information that shouldn't be trusted, along with organizations that promote specific misinformation (not disinformation) for profit without disclosing their financial interests. Remember that science is a process, and that new information must often displace earlier hypothesis and theories that are found to be incorrect.