As others have said the MMC isn't grumpy, he's an asshole. He's condescending, controlling and possessive. He meets his tenent for 1 mins and decides to mansplain life to her and is immediately possessive. He overracts and has no boundaries.  He barges into her house and when he sees she's naked he decides to stand their and leer at her. Then has the audacity to say "well it's my house" and tell her thr cops won't do anything. Okay major red flag! This is clearly an episode of Dateline. That is the kind of shit rapists say! And it's not even true. There are very strict laws surrounding tenants rights and privacy. 

The FMC is also awful but no where near the walking red flag he is.