Language changes all the time, and slang and casual talk language moves on even faster. Use the word 'porn' on its own or as pornography or with other specific sexual phrases and it is a serious issue but kitchen porn or otherwise it simply means feasting the senses on something.
'murder' is a terrible crime, ends someone's life and causes great grief to the family, but most people will talk of being so hungry they could murder a steak, or an ice cream or sometimes when someone does something daft or inappropriate we will say that we could 'murder' someone for doing/saying/not saying something, when everyone knows we have no such attention.