First, here’s the question that the author asked:

I was doing some research on the Spanish Civil War […] and I noticed in the timeline, that there was a nonaggression pact between the Soviet Union and fascist Italy, which it said strengthened economic relations. Can anyone tell me about this? I have severe doubts that the USSR would expand trade with a fascist power.

A pact between the Soviet Union and Fascist Italy. That does sound troubling, and we should very well be concerned learning about that for the first time; it is a serious accusation. Of course, chances are that anticommunists are either distorting the issue or making it up entirely, as usual, but it’s safest to withhold judgement until we have more evidence. Now, how do you think that communism101 responded to this?

The liberal democracies of Europe made similar agreements with Hitler and Mussolini before the USSR did, and shot down Stalin’s suggestions of an anti-fascist alliance in the 30s.

That’s… not the issue here. The original poster’s question was asking about the Italo–Soviet Pact and what we could tell them about it.

You trade with fascists every time you go to a store or pay your bills. What’s your justification and why doesn’t it apply to the Soviet people?

We frequently trade with anticommunists every time we got to a store or pay our bills. That is correct. But this topic is about the Italo–Soviet Pact, and a pact between states is a little bit different and more complicated than mundane transactions between individuals or a bill that we have to pay to businesses.

the USSR rightly determined that it was necessary to have some degree of economic relations with the capitalist world, why is it OK for them to sign peace treaties with Churchill and Roosevelt, both extreme genocidal racists, but unacceptable for them to do the same with Hitler and Mussolini?

Yes, fine, but the question was not asking if it was OK or not for Moscow to sign a pact with a Fascist government. The question was asking if we could tell the original poster anything more about the Italo–Soviet Pact. Here, this is exactly what the poster asked:

So I was doing some research on the Spanish Civil War on Wikipedia (already liberal source, I’m aware), and I noticed in the timeline, that there was a nonaggression pact between the Soviet Union and fascist Italy, which it said strengthened economic relations. Can anyone tell me about this? I have severe doubts that the USSR would expand trade with a fascist power.

‘there was a nonaggression pact between the Soviet Union and fascist Italy, which it said strengthened economic relations. Can anyone tell me about this?’ That is the question. Unless maybe the asker is experiencing some sort of moral or existential crisis, telling us that liberals co‐operated with fascists is unlikely to be of much help. If we want to demonstrate that socialism in one country is preferable to a bourgeois régime (be it liberal or fascist), this certainly wouldn’t be of much help.

So, what can we tell the author about this pact? Well, you are in luck, because I have a very credible answer right here. Quoting Andrei Yu. Sidorov in History of International Relations and Russian Foreign Policy in the 20th Century, page 190:

‘The sanctions were initiated by Britain, though already in the run-up to the conflict, the cabinet of S. Baldwin had firmly decided that it would under no circumstances go to war with Italy over Ethiopia. France, for its part, informed Britain that it was against imposing oil sanctions. The League of Nations never dared ban the sale of oil to Italy, thus missing the chance to stop hostilities. “If the League had extended economic sanctions of oil, I would have had to withdraw from Abyssinia within a week”, recognised Benito Mussolini later.

‘The Soviet Union took rather a cautious stance on the Ethiopian conflict. It did not have diplomatic relations with Ethiopia, while it had been quite closely co-operating with Italy. At the same time, Moscow could not ignore Mussolini’s aggression. “However much we wish not to spoil relations with Italy, we cannot but go up against the imperialist war… it masterminds”, wrote Maxim Litvinov to Stalin on October 5th, 1935.

‘The Soviet Union supported the sanctions against Italy but did not go any further, mindful of the position of France, its new ally. The USSR representative in the League of Nations was instructed not to be overzealous in the matter of sanctions and not initiate oil sanctions. In December 1935 the Politburo declined Ethiopia’s request for assistance with arms and military specialists. All those moves were aimed at avoiding a serious deterioration in relations with Italy and preventing its rapprochement with Nazi Germany.’

(Emphasis added.)

You don’t need to distract from the issue, appeal to liberal memes like ‘HORSESHOE THEORY’ or ‘RED FASCISM’ or even express perfect satisfaction with this turn of events. You exercise scrutiny, you try to get to the bottom of the issue (specifically through Google Books, as the case may be), and you think for yourself by determining which explanation is the most reasonable.

That is how you answer the question.