I don't really know why I'm a fan of Manchester United, I guess it's because they're very strong in the past. But, look at their performance now, they're playing like shit after Sir Alex Ferguson left the team.
Since Manchester United not able to be one of top team in Premier League and other teams mostly bullied Manchester United fans, I choose to not be a Manchester United fan anymore.
The performance of the team can indeed influence the fanbase as how can you support them if in case they have less to no more games to play. Though if we talk football, they will always have a match to play. However, if the team is continuously losing, the tendency is you will have no motivation to cheer them up as you are already disappointed to what may possibly happen.
Perhaps you can always hold upon your teams years past glories to hype them at some points of arguing with others team fans.
Just remember that at the end of the day, we are all just fans and the hard work is done by those athletes. We can glorify them by being proud of what they have achieved inside the field. But getting enemy out of bad discussion is I believe not a point in this sports.