The word "fearmongering" has seen wide usage among political commentators, particularly those on the left. It's one of those terms that I call a "red-flag indicator." Red flag indicators have little meaning themselves, but often tell you quite a bit about the person using them. Frequently, seeing such an indicator means you can stop reading, because what follows will be nothing but nonsense. For example, use of the words "moonbat" or "wingnut" tells you that the speaker/writer is well on the right or left respectively, and probably preaching to his own particular choir. Even words that used to have specific meaning, such as "neoconservative," are now virtually meaningless because of overuse & improper use, and now serve only as red flag indicators. There are all sorts of these types of words in political speech.
So what does serious use of the word "fearmongering" indicate? Generally it tends to reveal that the person using it is guilty of "stupidity-mongering," or "intellectual dishonesty-mongering." Almost everything labeled as "fearmongering" is simply reasonable concern over things that people are reasonably concerned about. Characterizing such concerns, or calls to take precautions as "fearmongering," indicates a lack of common sense or outright stupidity in some cases. People disagree about the severity of threats, especially ones which are difficult to quantify. But on public policy issues, looking at worst case scenario possibilities is just basic common sense. Prepare for the worst, hope for the best. That's rational policy.
Now it is true that threats are often politicized and used as a weapon against opponents. This is where the intellectual dishonesty element comes in. Scaring voters is a time-honored political tactic. How many campaigns are there in which one side doesn't say that if their opponent is elected, or the opposition is put/left in charge, things are headed for disaster? This tactic is used at all levels of politics and by all parties. The left & others who assert that the right is guilty of "fearmongering,"are nothing more than intellectually dishonest hypocrites. They are quite willing to scare voters on any issue where they think it will help their side.
The next time you see someone actually use the word "fearmongering" as if it were meant to be taken seriously, ask yourself this. Are they stupid, intellectually dishonest, or both?