Assuming we all agree that KF is reprehensible, the question is where is the line of moral obligation to stop supporting them. In the most reductive case, you could argue that anyone selling food or water to white supremacists is supporting white supremacy. Or that firefighters who put out a fire at a white supremacist's house are supporting white supremacy. But I don't think people generally consider that to be providing support, whereas they would consider, say, hosting a conference and paying white supremacists to speak at it as supporting white supremacists. So where is the exact line where it becomes "support"? It's ambiguous.
Cloudflare is in an unenviable position of being exactly on the line where moral obligation rests, further complicated by providing different products around hosting and DDOS mitigation. IMO, there is a clear distinction between hosting content and providing DDOS mitigation services, as the article suggests. And just as you wouldn't want your electric company unilaterally deciding that you were a white supremacist and cutting your power, I agree with CF's stance that they shouldn't be making extrajudicial decisions about which customers to use their DDOS protection.