"Pretentious" comes to mind, but I thought there was a word that specifically refers to pretending to like things of "high culture", or dislike the opposite. When I looked in the thesaurus I didn't see it.
Example uses:
I said I thought The Walking Dead was a stupid TV show, but I who am I kidding. I was just being ____. It was fun to watch and I love zombie shows.
You're being ____, pretending to like Mozart but listening to 80s rock ballads when no one around.
A person who pretends to be someone else could be referred to as an imposter. There are other synonyms, but this is particularly appropriate for someone who has infiltrated some group, such as more cultured peers. Another word you may want to look up is philistine, which is used to mean a person who is hostile or indifferent to culture and the arts. These came to mind from your question title, but it doesn't really fit your examples.
Your first example sounds like you need the word snob (eg I was just being a snob). It is synonymous with words like "highbrow" but it tends to carry the inference that someone has no right to think or act like that - perhaps a class traitor.
Your second example sounds like you need the word hypocrite - someone who deceitfully says one thing but believes or does the opposite.
Context is everything. Resistance is futile.
The context is a person describing his own ideas about himself.
"I was just being ____. It was fun to watch and I love zombie shows."
"I was just faking it."
