Sir Rod Stewart has spoken of his heartache over Glasgow Celtic fans who hurled missiles and insults at the club's players following a lost match on Sunday.RELATED: Rod Stewart reveals he needs another operation after complicated knee replacementDiscussing the behaviour of the football club's fans when speaking to talkSPORT, the superstar said: "I’m absolutely heartbroken, not only with the result yesterday but just all-round. I’m heartbroken and disgusted.