one of them is a player race and one of them isnt. Also theres no negative stereotypes of goblins. Its not a stereotype, its a type. the type is caleld "goblin"
Tho i admit, you should definitly be able to kill tiefling children just as much How else are you gonna roleplay that conquest paladin.
Goblins in D&D 5th are a playable race as well....
I think at least from my perspective is the goblins and their dialog and stories are far more interesting and deep than the boring tieflings.. literally they stand around the druid grove complaining fighting and getting in the way.. The goblins are busy partying and destroying the evil humans like goblins do but Larion humanised them to such a point people have started to feel for them.. And rightly so they are a sentient race..
In Warhammer goblins and orcs are hugely popular races these days with customers.. I think D&D folks are behind the times fantasy wise.