“It’s [the current year]!” or “this idea is from the dark ages.” Just because an idea is older doesn’t mean it’s bad. Not all new ideas are good.
“You can’t complain about what the current president is doing because the last president did it, too!” An immoral action is immoral regardless of who’s doing it.
“Why do you talk about X when Y is a bigger problem?” We all have causes we choose to focus on due to personal interest or experience. We can’t give all of our attention to every issue.
“You don’t really care about (unborn babies / the environment), you just want (to control women / a one world government to restrict free trade).” When someone tells you what their concern is regarding a certain issue, take them at their word and address their stated concerns until they give you a good reason to believe otherwise.
“Because this politician or pundit is guilty of one behavior I dislike, they must be guilty of any given bad behavior they’re accused of.” Someone may have any number of flaws, but that doesn’t mean they have every flaw.