Both Poland and Fernando Santos' side were reduced to 10 men in Friday's opener, but the defender took particular exception to Sokratis Papastathopoulos' expulsion
Both sides were reduced to 10 men during the co-hosts' 1-1 draw with Greece on Friday. But while there was little discussion over the expulsion of goalkeeper Wojciech Szczesny on the Polish side, a second yellow for Papastathopoulos for an innocuous-looking challenge provoked much controversy.
Olsson, whose team kick off their Euro campaign against fellow hosts Ukraine on Monday in Group D, confessed that the Greek red card had left him dumbfounded.
"You know the referees give cards away too easily at international level. So it will be key not to make any stupid tackles," Olsson told Expressen on Saturday.
"I thought the decisions yesterday were unbelievable. The red card was so cheap."
Sweden team-mate Pontus Wernbloom joined in the chorus of complaints against Friday's match official Carlos Velasco Carballo.
"You know if the referees continue like him we are going to have 20 cards in each match. But I hope he was having a bad day, that it was an isolated incident. I can't believe that the level of refereeing for the rest of the tournament will be that rotten."
Poland and Greece's draw leave the two tied for second place in Group A, with Russia topping the table following their emphatic victory over Czech Republic.