In my view, it is actually very unlikely for someone to actually be convicted of defending themselves inside their own home. They will most likely be charged and have to pay a lawyer lots of money and go through the stress of the court process, but they will most likely be acquitted in the end. Just consider a few recent cases where people were acquitted:
R. v. Peter Khill - summary of facts from the Ontario Court of Appeal decision on his case: [6] Mr. Khill and his then girlfriend, now wife, Millie Benko, lived in a single-story house in a rural area near Hamilton, Ontario. Mr. Khill was asleep at about 3:00 a.m. on February 4, 2016 when Ms. Benko woke him up and told him she had heard a loud banging. Mr. Khill listened and heard two loud bangs. He went to the bedroom window. From the window, he could see his 2001 pickup truck parked in the driveway. The dashboard lights were on indicating, to Mr. Khill, that some person or persons were either in the truck or had been in the truck
...
[7] ... Mr. Khill loaded the shotgun he kept in the bedroom and, armed with the shotgun, went to investigate the noises.
[8] Using techniques he had learned as an army reservist, Mr. Khill stealthily made his way through his house, ending up at the front door of the breezeway connecting the house to the garage.
…
[10] Mr. Khill said in a loud voice, “Hey, hands up.” Mr. Styres, who apparently had not seen Mr. Khill, began to rise and turn toward Mr. Khill. As he turned, Mr. Khill fired a shot. He immediately racked the shotgun and fired a second shot. Khill said he thought the deceased had a gun and was reaching for it.
Mr. Khill was acquitted by a jury. I'm not sure that I would have acquitted him ... sneaking up on a guy who's ransacking your truck and shooting him twice when he turns around does not seem like a reasonable use of force. Personally, while I think people should have wide latitude to defend themselves inside their homes, if someone was stealing from my car I'd call police but otherwise let them have whatever is in my car. Neither my life nor the thief's life is worth whatever is in my car.
But the point is he was acquitted. Also there's the case of Gerald Stanley, also acquitted. I could give lots of other examples, but it seems that unless the case is very clearly not one of self defence (like repeatedly striking someone once they're already unconscious, or stabbing someone in retaliation for them saying something offensive) people are most likely to be acquitted. In the case of your friend, I suspect that there was more to the story than what you heard if he was convicted.