Nicholas Anelka is being investigated by the FA after he made a gesture widely viewed as anti-semitic in France during goal celebrations in Upton Park today.
The gesture involves pointing one straightened arm downward whilst touching that arm's shoulder with the opposite hand, and has been condemned by Jewish groups as a "Nazi salute in reverse."
The gesture was invented by Anelka's friend and controversial French comedian Dieudonne.
It is defended as being anti-establishment but authorities are considering banning it in France and French Interior Minister Manuel Valls said he is considering banning performances by the comedian altogether.
More top news
Activists, including a young woman wearing a head scarf, spoke out in turn in front of the cameras assembled to hear leader Paul Nuttall.
Mr Farron's bizarre comment was made to an activist who came to watch the party leader speak in Cambridge on Thursday.
The US actor starred in Disney's 2004 film Miracle, chronicling the US men's hockey team at the 1980 Winter Olympics.