"Peer review" has a way of filtering out politically incorrect science, either by limiting funding or by hindering publication.
Peer review basically tends to support whatever is the dominant paradigm. Every career researcher has a file drawer full of data which he worked hard to collect, may be methodologically very sound, is interesting to him, may be very important to science--but which is unpublishable because it does not conform to the prevailing assumptions.
This pervasive pattern has already clamped a veritable death grip on the global warming hypothesis.