It's rude to use a service without paying for it
Silas can't watch Stranger things because he lacks a Netflix subscription, but he sees the log in information for his friend's netflix account on the table.
Silas wants to watch Stranger Things.
Silas asks his friend if they could watch stranger thing while he's hanging out at his friend's house.
Silas uses his friend's log in information to watch Netflix on his tv.
Silas and his friend bond over watching the show.
Silas friend yells at him when he discovers Silas using his account.