Did Frances Coppola, a senior journalist at Forbes, post the following tweet?
@shoerster I bet they did. I suspect anti-immigration people of organising the Cologne sex crimes. Fastest way of getting borders closed.
The screenshot is from a tweet by Rita Panahi, and the allegation was also made in the Herald Sun (paywalled), a major Australian tabloid newspaper, in a column by Panahi called "The sexual assaults in Cologne show even the harshest facts must be faced" (January 11, 2016):
Meanwhile Forbes senior journalist Frances Coppola posted a comment alleging a vast conspiracy: “I suspect anti-immigration people of organising the Cologne sex crimes. Fastest way of getting borders closed.”
I also came across an article in the neo-nazi site The Daily Stormer (Wikipedia description) Forbes Journalist: “I Suspect Anti-Immigration ppl of Organising the Cologne Sex Crimes”, which has an archive.is link of the alleged tweet. However, archive.is explicitly denies that it can be trusted not to doctor or alter pages:
How do end users know that archived pages aren't doctored or altered?
Many pages are altered. Main reason is to remove a popup or login box covering the content.
I'm not that skeptical that some people allege a false-flag attack: for example, this tweet and this one are non-parodic tweets (favorited and retweeted by antisemites) claiming that Jews masterminded this attack by asylum seekers.