Communist and fascist states have a lot in common. They're both one-party dictatorships. This is the basis for the assertion that communism and fascism, and thus communists and fascists, are similar.
But it does not follow that communists and fascists as individuals are similar -- unless we're speaking about the government officials in both kinds of states, or long-term party bureaucrats where they are opposition parties, who probably do/did have a lot in common.
The key difference is this: communists profess to want a better world for all of humanity: a world without war, unemployment, racial discrimination. They are -- or used to be -- thoroughly committed to the project of modernization, bringing backward, primitive people into the modern world. They wanted equality for women long before it became popular. They fought against racial discrimination in the US back when lynchings were not an uncommon thing.
Fascists, on the other hand, are explicitly tribalists: they want to see the victory/domination of their race/nation, and in the extreme, are willing to exterminate people they see as racial inferiors. (Of course, there are shades of fascism: Mussolini was far less horrible than Hitler, Franco also -- their material circumstances didn't really allow them to have world-conquering ambitions, and they didn't achieve power by demonizing the Jews.)
Fascists are happy with continuing things like the subordination of women. (Modern fascists, of course, have, like everyone else, moved with the times, or some of them have. I read recently that a branch of the Ku Klux Klan has announced it's open to homosexuals and Jews. Probably most of the idiots flirting with the 'alt-right' wouldn't openly admit to wanting women to return to Kinder-Kuche-Kirche but most of them seem pretty unhappy with women as they are now.)
Although fascists have some common roots with the traditional Old Right, it's not useful to see them as just extreme Right wingers. They aren't really conservative: Hitler did not want to conserve the German monarchy, for example: he was a thorough modernist, supporting development in science and engineering. Fascists did not appeal to traditionalists, as conservatives do, but to people who were radically disappointed with their lot -- due to defeat in war, and/or the economic situation. The Nazis, in particular, stole the Socialists' clothes,although their ultimate aim was to defend the capitalist order (although not the free market). They studied, and imitated the Leninist party model: a combat party, not an electoral machine.
Communists not in power are wrong-headed, naive, willfully blind ... yes. But their aims are not outright evil. Most of them are laudable. They don't sit around and cackle about how wonderful it will be when we are all mindless tools of the all-powerful state. In fact, they believe that eventually, there will not be a state ... that it will wither away.
You can task them with being willing to apologize for the evil of communist regimes in power, and I think that's fair enough. But before you do ... be sure you're not a pot calling the kettle black. Most of those Americans who were aware of American foreign policy behavior during the Cold War (admittedly a minority) did not disapprove of our overthrowing a democratically-elected government in Iran, or supporting the overthrow of a democratically-elected government in Chile, and their replacement by bloody dictatorships.
So the rationale of communists for the nastier side of communist regimes -- that sometimes you've got to play rough -- is one that is shared by everyone. And the rationale that I've seen for the rule of the Shah in Iran, or Pinochet in Chile -- that their governments actually moved their countries forward economically -- was also the same rationale used by communists when talking about Mao or Castro or Stalin.