"is the issue less that he didn't sign and more that he took off on the petitioner?"
As I recall, the petition went out and he tweeted that he would have signed, had he been asked. That prompted replies that it wasn't too late, he could still sign. He then backed off, saying he couldn't possibly sign something he hadn't read and didn't know about.
Signing, or not, isn't a problem.
Claiming you would have signed, if only you'd been asked, then backtracking and attacking the people who offer you that option is disingenuous.