There's plenty of evidence showing that manufactured trans fatty acids are harmful. However, Conjugated Linoleic Acid is a naturally-occurring trans fat, which has several studies showing that it might have anti-cancer properties, as well as helping in weight management.
Inhibition of carcinogenesis by conjugated linoleic acid: potential mechanisms of action.
Conjugated linoleic acid (CLA) is composed of positional and
stereoisomers of octadecadienoate (18:2); it is found in foods derived
from ruminants (beef and lamb as well as dairy products from these
sources). When a mixture of isomers is fed to experimental animals,
chemically induced tumorigenesis of mammary, skin and colon is
J Nutr. 2002 Oct;132(10):2995-8.
Although CLA isn't an essential nutrient, the OP actually made two claims, the other being about CLA having no benefits.