Ideologue is probably the word your looking for, since your specifically looking for a word that describes blind allegiance to ideological or political forces.
- an often blindly partisan advocate or adherent of a particular ideology
Partisan also is a pretty good word for what your describing itself. Typically its used now by politicians or media organization to slander each-other though, so its true meaning has become muted over the years due to over use.
- a firm adherent to a party, faction, cause, or person especially : one exhibiting blind, prejudiced, and unreasoning allegiance political partisans who see only one side of the problem
Sycophant is also a pretty good word to describe people like that if they have something to personally gain or lose.
- A person who attempts to gain advantage by flattering influential people or behaving in a servile manner.
- A tale-bearer or informer in general.
- A parasite; a mean flatterer; especially, a flatterer of tyrants and great men.
It also has a connotation of someone who is slanderer, accuser, calumniator, etc.
There are also words like: Fanatic, and Zealot