Yes, "racist" jokes are inherently racist. The types of jokes that this question is referring to revel in negative stereotypes and hurtful imagery against particular racists, one of the very definitions of being racist. To suggest that a joke called "racist" might not actually be racist is more than silly.
Racist jokes, like rape jokes, can be humorous if the joke is at the expense of the bad guys (i.e. the racists or the rapist.) If the punchline comes instead from disparaging people of a different demographic than it is a negative joke. Also, a "racist" joke told by someone within the subject demographic to others with the subject demographic, it may be, rather than an offensive insult, a way to bond over joint understanding of their culture.