Even though I initially thought that UT was calling Othello out because Othello had possibly proved in the past to have the same misguided curiosity towards humans (which is what the very original idea of UT’s BD project was initially), now I wonder if this wouldn’t rather be a Shakespeare reference? 

For those who don’t know, the tragedy Othello is about a Moorish man living in Venice who’s tricked into believing that his wife is having an affair with his Lieutenant. So he kills her out of jealousy, before realizing the truth and killing himself as a result.  

So if Othello in Kuroverse is supposed to be a reference to this tragedy, that’d mean our boy here became a Shinigami because he killed his wife. 
Meanwhile, if we’re considering that UT’s strong attachment to the Phantomhive family roots from the possibility that he had strong feelings for Claudia 

and that ultimately he wants them all back because…

• he doesn’t want his connection to the P family (to Claudia in particular?) to disappear
• or because he promised Claudia he’d protect them all and he doesn’t want to fail his promise to her

 …then I’m wondering if this isn’t what UT is referring to when he’s calling Othello out, as in, “I’m doing this out of love and you should be the last one to criticize me on the subject considering your own circumstances.” 

Since some readers often have the wrong timeline in mind though, please remember that UT killed himself way before Claudia was even born and he met her after he deserted the Shinigamis, it’s not like he became a Shinigami because she died. So it’d go like this when it comes to Othello vs UT:

• Othello: killed himself because he killed his wife
• UT: killed himself, deserted, fell in love, lost the woman, decided to experiment about bringing back the dead
• hence ch142 and UT telling Othello to back off about saying he lost his mind on the subject (sensitive subject for him and all).

TL;DR