theoretical (and not thinking about practical problems)

dogmatic, opinionated

put forward as dogmas; (of a person, statement) expressing opinions in an arrogant way

dictatorial, opinionated

an animal that is the young of a horse and a donkey; a slipper without a heel

stubborn

stubborn

pig-headed, stubborn

decided and fixed; (of opinions, habits etc) fixed and not to be changed; unmoving; a group of games (in tennis etc); a group of similar things; the position (of the body, clothes etc)

decided

demanding and enforcing obedience; severe; strict; the back end (of a ship or boat)

serious, authoritarian

(of a person) having a strong, determined will; difficult to deal

obstinate, unyielding

not prepared to make any compromise

stubborn

not hesitating

steadfast

not becoming less in force, degree

merciless

(of a person) determined to have one's own way; intentional

stubborn, obstinate