Following on:

If the OPs goal is to let CX know of your dissatisfaction, definitely write them another form or send an email. Because it sounds to me like you gave it to the ISM, and I'd bet heavy odds it won't be passed to CX mgmt if that's the case. Instead the ISM probably tossed it.

Without any real proof of racism, I recommend sticking to the facts. It sounds like service sucked and the ISM was rude. CX is a bureaucracy but they are (ostensibly) concerned about poor/rude service on board. The ISM raising her/his voice to you in front of the other passengers isn't acceptable service standards to me. I'd focus on how you felt humiliated but leave the racism / favoritism towards white people tone out of it. I think your argument will be much stronger. However, don't expect much...if you've trolled around this forum you'll find people having to follow up multiple times with CX just to not get a canned reaponse. And some of these guys had obvious "compensatory" problems, like broken IFE.

Good luck. No matter what it's terrible the ISM made you cry!