Developers have the right to complain about third-party packages (and that is not the end of software freedom)
People take pride in their work and are attached to it emotionally. As far as my basic understanding goes, this was pointed out by Karl Marx (among other things) in his theory of alienation way back in the 19th century. I think most people have experienced this feeling in their lives too. In FOSS, the emotional connection is even more important, as most of the time there is no other benefit to the contributor than that pride.
If the person thinks that the product of their hard work is made worse by a third party, they will be upset. If I was a chef and the waiter messed up the plating I meticulously did, I would not like that. If I pulled a espresso shot, paying attention to all the variables, selecting the most delicious beans and it was turned into an ice coffee mixed with two table spoons of sugar and filled to the brim with heavy cream; I would be upset.
All things aside, people have right to