An anarchist is fighting against military/police. A fascist belongs, or wants to, to military/police. An anarchist is fighting against people who hold some power. A fascist is fighting against people because of their religion or origins. An anarchist likes to vote and discuss. A fascist likes to follow orders. An anarchist tends towards decentralization. A fascist tends towards centralization.
This are only some differences but spoiler alert : anarchist and fascist are not the same. They do not act the same way, they do not think the same way.
I understand that you hate them both, it is your point of view, and it’s okay. But please, follow my advice : avoid trying to justify it with sentences as universal and strong as “There is no practical difference”, it makes the whole thing ridiculous.
In the end, saying there is only “one viable […] party”, and even believing in a party itself, are also part of the problem imo. If you truly believe in this sentence, no wonder why you dislike anarchists and why they probably dislike you. But does it imply that either you or them are fascistic ? And if yes, did you considered that it could be you, who are defending a single “viable” party as the only solution, hating on every other option ?