Patrick had been in the U.K. to support his former on-screen wife Meghan Markle at her wedding to Prince Harry, along with several other members of the cast.
However, on his way home, he revealed he got into a conversation with a woman at Heathrow airport, who commented that he had been looking "chunky" in photos taken on the day.
The woman then went to sleep, at which point Patrick took a photo of her and posted it on his Instagram page, sharing her remarks and noting: "And... scene."
When people began commenting on the photo by suggesting that Patrick had been just as bad by sharing a photo without her consent, possibly with the intention of casting aspersions on her appearance, he later took down the photo and posted a lengthy statement.
He wrote: "Yesterday I posted a photo of a woman who did some casual body shaming of my wife and I in the airport.
"My intention was solely to put a face to the people who think that sort of glancing commentary is necessary, helpful or funny. Some of the comments on the post instead said I was being a bully and should have taken the 'high road' (some also doubled down on the body shaming. Thumbs up guys!)
"I thought it over and agreed and took it down, not because I felt the woman was right or fair or undeserving of being called out, but because any sense of being a bully or lashing out felt wrong."
Addressing the "outlets with a lot of extra time on their hands" who have been asking him for comment, Patrick continued: "I'm no bully. What that woman said to us was offensive and unnecessary, but I should have told her she was rude and out of line and left it at that. I'm sorry I didn't. I was too shocked and annoyed and Canadian — so I avoided the confrontation. Again, I'm sorry.
"Now if you see the original post on any media outlet, just know that they are choosing to take a relatively small indiscretion and make it worse. Not for me. Because I promise you once I hit post on this message it will be out of my mind forever. But it will make whatever bullying or embarrassment I might have caused for that woman far worse for a far wider audience."
The actor concluded: "Let's just finish with a quick summary. 1. Don't talk shit about the way people look. You have no idea what's going on with them, and your commentary will always make their day worse not better.
"2. If someone does. Don't use the internet to settle scores. Tell them right to their face and in public that they're part of the problem and not the solution.
"3. Believe pretty much nothing you read in magazines. Good or bad. The machinery runs on misfortune and oversimplification.
"4. Be cool to yourself and others at every opportunity. Life is too short for all of this."
Patrick isn't the only "Suits" actor forced to explain himself lately, with co-star Rick Hoffman explaining that the "weird face" he pulled during the royal wedding ceremony was down to one mystery guest's "halitosis" rather than any sort of discomfort with the event itself.