Ginbey was struck on the back of his hand by the lemon just moments after the club's 30-point win over Essendon a fortnight ago.
The lemon flew about 30m in the air before hitting Ginbey, who last week expressed his shock at the incident and said it was fortunate it didn't hit him in the head or the eye.
Vision showed the thrower also had a second lemon in his hands, which he didnt use.
The fan, who was not a West Coast or Essendon member, has copped a five-year ban from all AFL and AFLW games.
"You can't do that, so I think it's the right decision," McQualter said on Thursday.
"We've got to protect our players."
Ginbey could miss the rest of the season after tearing his left quad during last week's six-point loss to Port Adelaide.
The 21-year-old is West Coast's best defender and McQualter is backing his team defence and pressure further up the field to help cover the loss of Ginbey, who recently signed a contract extension.
West Coast face North Melbourne at Optus Stadium on Saturday, meaning there will be plenty of heat on key backmen Tylar Young and Rhett Bazzo to contain the likes of Nick Larkey, Jack Darling and Cooper Trembath.
McQualter is expecting North to come out breathing fire after they copped a 124-point thrashing by Fremantle in Bunbury last week.
The Kangaroos were held scoreless in the second half as Fremantle piled on 19 consecutive goals to post the club's biggest-ever win.
North Melbourne's best win this season - a six-point victory over Gold Coast - came a week after they lost to Adelaide by 68 points.
The Kangaroos also rebounded from a 49-point loss to Geelong to push Sydney all the way the following week.
McQualter has told his players to brace for a physical contest from the Kangaroos.
"We've done like a little bit of research around every time they've had a loss this year, maybe a bad loss, the way they've turned up the next week has been really quite fierce," McQualter said.
"So that's what our expectation is - they'll turn up.
"Every player has pride in performance and team, and I'm sure they'd be disappointed with their game last week.
"But the expectation is that we'll get a red-hot Kangaroos turn up on Saturday afternoon."
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