The 47-year-old from Paisley acquired instant hate-figure status amongst his former followers in Burnley in 2010 when he broke an unwritten Lancashire taboo by joining Bolton Wanderers.
His response to the massed chants of 'Judas' he endured on his return was the insistence that a more appropriate biblical comparison should really be Moses, as he had previously led the club to "the promised land" of the Barclays Premier League.
But this gauntlet of hate, to borrow from tabloid vernacular, never came to outright violence, and was witnessed only twice, both times on derby day. For the record, the former Wigan Athletic manager regards it as a hugely depressing departure from the norm that the Celtic manager can expect to be spat at and have coins hurled at him by Aberdeen supporters while sitting quietly as a neutral at a national semi-final.
"I went twice there [Turf Moor] to play games," recalls Coyle. "I never went to scout them because we kept Bolton up. But I was out at games all the time and I've never experienced anything like that. If people want to come and have their opinion or have verbal abuse, I'm not saying it's right but it happens. But this was more than verbal abuse and that's way beyond the level of what's acceptable and allowable.
"It's got progressively worse," he adds. "There was a spell after I left Scottish football when it wasn't particularly nice between Celtic and Rangers and you're hoping that it would've moved on. But the thing that alarmed me was that this was nothing to do with Celtic or Rangers, this wasn't a game that concerned you, it was watching the opposition. Whoever did it is a total idiot."
There had been talk in the hours after Saturday that such incidents may eventually force the Northern Irishman out of the Scottish game but, for whatever reason, openings in the top league south of the border have not exactly been forthcoming. Coyle, who has turned down a few approaches to continue coaching in England after his departure from Wigan, points out that recent history shows even the grandees of the Scottish game struggle to walk into jobs in the English top flight.
"When they are in full flow on a Champions League night I don't think it does get any better than Glasgow Celtic," says Coyle. "The difficulty is that every week isn't like that. In England it is.
"You don't know what goes on behind the scenes, who is on this or that shortlist. But probably the difficulty comes back to how the league is perceived. Alex McLeish was an outstanding manager who did fantastically well at Rangers in difficult financial circumstances, and all Alex got was a Birmingham team in the bottom three, fighting for their lives to stay in the Premier League.
"Gordon Strachan was outstanding at Celtic and still had to go into the Championship with Middlesbrough. From my own experience, I came from doing a good job at St Johnstone to the Championship, then had to earn the right to go in."
Coyle was ostensibly speaking to promote William Hill Scottish Cup fifth round weekend, which begins on Friday night with Rangers at home to Dunfermline Athletic and sees Celtic take on an upbeat Aberdeen side on Saturday. Both Glasgow giants will feel rather unfulfilled if they cannot conjure an extended cup run, but Coyle witnessed Rangers in the flesh recently at his former club Airdrieonians and feels they must be regarded as outwith the top rank of favourites to lift the cup.
"If I was judging it on that Airdrie-Rangers match then I would say that they have some very good players, some very good young players coming through, but my own personal opinion is that I don't think they would be one of the first four or five favourites for the Scottish Cup," says Coyle. "Can they win it? Of course they can - with a little bit of luck. No.1 and No.2 [Celtic and Aberdeen] are playing against each other, so one of them has to go out to create a clearer path for somebody. But if you are asking me are they in that position, in terms of the strength of their team against others, I would have to say no."
Consequently he questions whether anyone at Ibrox should be hankering for the first Old Firm game for two years in the event that both teams reach the quarter-finals unscathed. "With Celtic being so strong right now, the odds are that they would win the game," he says.