There are several factors to how people would have treated communists in the United States following the first world war. The first factor is location. Depends where you are located. Also, depends on your neighbors and how open you are. In any case, say you were open about being communist, things would have been extremely bad. Americans viewed communists as conspirators trying to overthrow the American government. There is a ton of coincidental evidence to support this thought, too. Russia left the war following the Bolshevik Revolution, making it appear ad though they were trying to topple the West. Furthermore, with people being extremely on edge in the US, things were bound to happen. Bombs exploded in major cities, leading to the Palmer Raids. These raids were conducted in trying to find the bombers, with no success. However, they targeted recent immigrants and radical political groups, such as communists. Since Americans blamed immigrants for radical thinking, this naturally lead to a change in immigration laws to restrict immigration from Eastern Europ, namely Russia.