Rubbish got said with extremes of Marxism, inflexible ideology (9)

'inflexible ideology' is the definition.
The definition and answer can be both related to thinking as well as being singular nouns.
Perhaps they are linked in a way I don't understand?

'rubbish got said with extremes of marxism' is the wordplay.
'rubbish' indicates anagramming the letters (a poor quality or rubbish spelling of the letters).
'with' means one lot of letters go next to another.
'extremes of' suggests removing the centre (only the letters at the extremes of the word).
'marxism' with its middle taken out is 'mm'.
'got'+'said'='gotsaid'
'gotsaid' put after 'mm' is 'mmgotsaid'.
'mmgotsaid' anagrammed gives 'DOGMATISM'.

Can you help me to learn more?