I also think the OP is missing one key thing. The cultural component.
It may be taboo to mention, but if we're talking about long term relationships, there may a people who want to have children that look like them.
Again, I have no issues dating or marrying any ethnicity, but to not be aware of that is naive.
Remember that the OP's original article focuses on dating apps that target the gay community. So the "children who look like them" argument isn't going to be a factor in this.
The other problem with this line of thinking in relation to the OP is that the majority of the examples are in regards to online dating where people are putting "No Asians/No Jews" etc... in their profiles. Going back to heterosexual relationships and excluding those who are using apps like Tinder just to "hook up" or people who are on these sites and don't want kids/already have children, it would be one thing if these people thinking about future children were posting "I only date white men/women", but in this case they are excluding certain ethnic groups while including others. So these people who put "No Asians" or "No Black Men" may or may not have issues dating a man/woman from say Ecuador or native ancestry from Bangladesh.
While you're right that there are some people who do think like this/are thinking this way, this isn't the issue in most cases/the main examples being discussed in this topic.