soft money was going into political campaigns.
legally they're allowed to burn what they wish. they're breaking no known laws. if the burning violates any fire ordinances then no such burning should be allowed. as long as no one is being hurt, burned or anything of the sort, the burning of a cross would be protected as free speech (even reprehensible speech is still protected).
there are conditions under which the burning of a cross could cross the line into being an overt threat and could be prohibited on that basis. that would probably only be the case if it was done in a location or near a location that was culturally significant - such as adjacent to an african-american church or in a park in a predominantly african american community.
of course placing a burning cross in someone's yard is not "at a rally" and is most certainly both offensive and an overt threat and can (and should) be prosecuted.
throwing anything at a moving vehicle is considered dangerous and illegal because it can impair the drivers ability to maintain control. it's not a smart, or kind, thing to do.
throwing snowballs at a parked vehicle only becomes illegal if you cause damage. a misdemeanor in most courts if it's under $500 in damage. still not smart.
why don't you find something less fragile to throw snowballs at? like a sibling, friend or wall.