This is true, at least, in the field of sex differences. Liberals asserted for many decades that there were no significant differences between men and women. Any differences that did exist they dismissed as being a product of socialisation. Their aim was to remove "discrimination" so that men and women would become the same. They wanted to do this because they want people to be created through individual choice, not by their inherited sex.
But science has undermined the liberal position. It has shown that conservatives were right all along: that there are natural differences between men and women which can't simply be erased by social engineering.
Here is a quote from a new bestseller book by Dr James Dobson, summarising what has happened:
The unisex movement prevailed until the late 1980s when it fell victim to medical technology. The development of magnetic resonance imaging and PET (positron emission tomography) scans allowed physicians and physiologists to examine the functioning of the human brain in much greater detail.
What they found totally destroyed the assertions of the feminists. Men's and women's brains looked very distinct when examined in a laboratory. Under proper stimulation they "lit up" different areas, revealing unique neurological processes. It turns out that male and female brains were "hardwired" differently, which along with hormonal factors accounts for behavioural and attitudinal characteristics associated traditionally with masculinity and femininity.
How have liberals reacted to this news? Mostly they have continued to push for gender role reversal, which is logical enough given their first principles. But they have had to do this knowing that they are going against nature. There are a few liberals, though, who have rethought things and decided that gender difference is OK. Michael Moore in his latest book, for instance, urges his fellow liberals to now accept that it's normal for men and women to behave differently.
If you're interested I've also covered this issue in a Conservative Central article, When science is a friend.