Citizens United has to be the most inaccurately cited case. It did not 'allow unlimited corporate political donations by classifying them as "speech"'.

It ruled that the federal government was wrong to restrict the speech rights of some groups while allowing other very similar groups to still retain their rights. One of the major examples of this was the media industry. A for-profit newspaper company could spend whatever amount of money it wanted to on political speech. An identical company in a different field could not. This, the court ruled, was unconstitutional.

It also did not grant corporations personhood, the other thing people like to state that it did.