President Biden's having a crappy day -- just as he was trying to make a very serious point about inflation and the economy ... a bird decided to drop a deuce right on his fancy suit.JB was delivering a speech Tuesday in Menlo, Iowa -- within what he described as a barn of some sort -- where POTUS was talking about infrastructure, inflation and figuring out a way to lower costs for Americans ... all in the framework of the farming industry.While he was talking about seeing the work they do there and giving these folks praise, something fell down...