Karl-Georg Wellmann, a member of Chancellor Angela Merkel's Christian Democrats and head of the German-Ukraine parliamentary group, had called Russia a "warmonger" earlier this year for supporting separatist forces in Ukraine, which Moscow denies.
Wellmann, who has called for tougher sanctions against Russia, told Reuters he spent the whole of Sunday night in the transit section of a Moscow airport and flew home the next morning, having been told he was not allowed to enter the country until 2019. He said no reason was given.
Germany protests 'unacceptable' ejection of Merkel party MP from Moscow | Reuters

So, Russia hits back and it doesn't help the dialog.