Adjective
divisive - Causing disagreement or hostility between people, tending to disrupt unity or harmony.

The election was fought over the deeply divisive issue of immigration, and people on either side of the issue can't see things from the other point of view.
preposterous - Contrary to reason or common sense; utterly absurd or ridiculous.
When Sandy's stock broker called and suggested that he sell half his stocks because he felt the market was overvalued, Sandy thought the idea was preposterous - but it turned out that his stock broker was right.