I think the more obvious comparison is Ned Stark in game of thrones tbh. The audience stayed through that and into future seasons despite the fact that Ned Stark very much felt like the main character of the show if you hadn't read the books. They even spent multiple episodes heavily featuring the character who had him killed and this character was actually just the worst. I think the show can get through killing Joel as long as they do it early in season 2. It gets harder and harder the longer he's viewed as the "main character". Glenn was a major character in the walking dead for almost 7 years when they killed him so of course the response was a little different. Not to mention the quality of the walking dead had been sliding for years before this happened