(Going off the assumption that Grindelwald kept Graves around like Crouch did Moody in GoF)
At some point Grindelwald has Graves bitten and turned into a werewolf/vampire/other as with the stigma on beasts in the USA (see Tina automatically assume Newt is writing an extermination guide when he mentions writing a book on creatures) Graves knows that even if he manages to escape the life he knew is over. Movie happens, Grindelwald gets caught and they find the real Graves but, sure enough, if he isn't getting judged for Grindelwald's actions while using his form it's for the fact he is now classified by MACUSA as a dangerous beast.
Given everything that's happened Graves thinks he has the right to be a bit depressed but it's a little hard to mope when whenever he gets in the same room as one Newt Scamander the other man basically turns into the biggest fangirl ever over him (and it happens often as they're being questioned about related events...and Seraphina Picquery + Tina might just be the matchmakers from hell)
Bonus for Graves having obvious (possibly facial) scars from the turning.
TL;DR: Newt is a major fanboy for all magical creatures and Graves can now technically be counted as such.
Original!Graves/Newt - Creature!Graves finds a fanboy
At some point Grindelwald has Graves bitten and turned into a werewolf/vampire/other as with the stigma on beasts in the USA (see Tina automatically assume Newt is writing an extermination guide when he mentions writing a book on creatures) Graves knows that even if he manages to escape the life he knew is over. Movie happens, Grindelwald gets caught and they find the real Graves but, sure enough, if he isn't getting judged for Grindelwald's actions while using his form it's for the fact he is now classified by MACUSA as a dangerous beast.
Given everything that's happened Graves thinks he has the right to be a bit depressed but it's a little hard to mope when whenever he gets in the same room as one Newt Scamander the other man basically turns into the biggest fangirl ever over him (and it happens often as they're being questioned about related events...and Seraphina Picquery + Tina might just be the matchmakers from hell)
Bonus for Graves having obvious (possibly facial) scars from the turning.
TL;DR: Newt is a major fanboy for all magical creatures and Graves can now technically be counted as such.