‘Understand’ is a Verb of Success

Here I encountered the following sentence:

However, most people understand their side is good and the opposing side is bad, so it’s much easier for them to form these emotional opinions of political parties.

This sentence features a misuse of 'understand.'  'Understand' is a verb of success.  If you understand something, then it is the case.  For example, if you understand that both 2 and -2 are square roots of 4, then this is the case.  Otherwise there is a failure to understand.  'Understand' in this respect is like 'know' and unlike 'believe' or 'think'.  My knowing that p entails that p is true.  My believing or thinking that p does not entail that p is true.  My understanding that my side is good entails that it is.  The above sentence should read as follows:

However, most people THINK their side is good and the opposing side is bad, so it’s much easier for them to form these emotional opinions of political parties.