If you live in the USA, the first amendment protects your freedom of speech from the GOVERNMENT. It does not protect you from people responding to your speech. In short: people can say what they'd like but they shouldn't cry FREEDOM OF SPEECH as if that means something when it comes to people responding to racist bullshit.
Exactly!^ Also the first amendment includes that if that speech becomes harmful then there will (or should) be consequences. For example, you are allowed to say the word “fire”, you are allowed to point out when there is a fire, but if you are in a movie theater (or somewhere else) and lie and say there is a fire (in some sick attempt at a joke) you could be prosecuted for it because you could have potentially caused injury to the people around you.
If you post racist photos, that dehumanize people, that is harmful and should be punishable, in some way. The first amendment is supposed to protect us from those who would initiate threats (and more things) so when these ignorant and or racist people post these photos that fetishize Native women and dehumanize Native Americans they are promoting harm towards Native Americans and therefore cannot hide behind the first amendment.