All it takes is one idiot to act on those words and the humour ends in an instant.Not offensive. Deliberate ignorance is just humorous to me.
That one single incident, even if it's spray painting something on a wall which is derogatory incited by those words ties the person who made the statement guilty of a hate crime.
Keep in mind that ignorant statements like that garnered support for the attempted genocide of Jews, Roma and Slavics in Europe and more recently lead to the bloodbath in Somalia.
Giggling and dismissing statements of that sort can make you indirectly responsible for any harm that may occur to the targeted group.
Doing or saying nothing only gives those who take the words serious a green light to continue being first class azzholes which can easily snowball into bloodshed.
It's nothing to giggle about.