The solution is obvious mang.
Shoot him. He's different and must be purged.
In a more serious note, if it was a conversation you didn't want others to butt in on, you should of had it in a more private area. You won't have a romantic conversation with a lover through megaphones, likewise you shouldn't have "private" conversations in public spaces. You don't own the space around you, and you're responsible for whatever you emit and others overhear. If your comments spark outrage from another person, you've only yourself to blame for saying those comments within earshot.
Also, for comments about racism being inborn, it's not exactly true. Discrimination is suspected to be inborn, but racism is not. Babies in the pre-operational stage of development will discriminate against individuals dissimilar to them, while sympathizing with individuals similar to them. This similarity can be as simple as liking the same snack. It's important to note that babies at this stage are not proven capable of distinguishing what they themselves look like. So they won't discriminate based on color until they establish a sense of self, in which case the inborn trait of discrimination can be applied to skin color.
However, discrimination based on color is not necessarily racism. I'm uncomfortable around black people, so I discriminate based on color, but it's not because of racism. I'm uncomfortable because I didn't see many, if any, black individuals growing up (I think I only knew one black person up through 7th grade), so I have trouble dealing with them in face to face situations because I have a lack of exposure to them compared to other "races." However, if I assumed that all black individuals are illiterate, then I'm wading into the world of racism. If I make a general assumption about a "race," then I have a prejudice, which is the key aspect of racism. Prejudice is discrimination by having a pre-judgement about something, the key facet being that it's a previously made assumption, which requires conscious thought, which implies a learned behavior. Racism is having a pre-judgement on a "race." So basically, all racism is prejudice, and all prejudice is discrimination, but not all discrimination is prejudice, and not all prejudice is racism (think how all squares are rectangles, but not all rectangles are squares, it's the same concept). From this, you can conclude that discrimination is an inborn trait that can build towards a learned behavior of prejudice, which in turn can be a learned behavior of racism.
tl;dr: Racism is learned behavior because it's pre-ordained thoughts, which implies learning. Discrimination is inborn, as it's demonstrated even among individuals who are incapable of retaining memory, which makes learning impossible.