Least I think I get it.
The Heinz ad isn't actually supposed to be a same sex couple at all. It's a New York Deli man acting as Mum and therefore kissing everyone including husband and that's the joke.
We don't know what the complaints were - they were probably from both sides of the argument.
The delicious irony is the pickle (probably Branston, HP or Tesco's own brand) that Heinz have manouvred themselves into.
Being an American company they can't issue a press release saying the ad was not a good representation of a same sex family - they'd end up with a US Christian boycot (the US market is bigger), they can't become a Stonewall champion - same reason.
It's a rather delicious irony but does at heart show they lack LGBT sensitivity to put the ad in the first place and I wouldn't like to be the Ad Agency that created the ad right now!