I think that calling this "whataboutism" is wrong. It is good to weigh the actual risk something presents and putting it into perspective.
The truth is that terrorism is a minor threat compared to others in our life yet a disproportionate amount of effort and fear stems from it. Your assertion that they would eventually take over is an overstatement. There have been countries under occupation with strong resistance movements that were orders of magnitude more active and disruptive and had far more popular support than the terrorist threat we are facing now, and those movements by themselves did not manage taking over, it seems unlikely terrorists would manage this now.
> (Compare for example with the reaction to the AIDS epidemics in the early 1980s. The lazy whatabout-ist could have said (and indeed did say): "Oh AIDS just affects a few gays and needle-sharing heroin addicts, whatabout the orders of magnitude more who die of the flu and cancer, no need to worry about AIDS".)
In a way, this example is also flawed. If, a comparatively similar amount of effort and research would have gone into developing cures and treatments for the other diseases, the benefits would have also been, probably, order of magnitudes greater. Would that not have been a logically superior choice?
On the other hand, I find very interesting you approaching this as a disease that has to be controlled and quarantined so it does not spread, it might have some merit. But we are not proposing ignoring the issue, but acting in a way proportional to its actual threat level, some way that the costs of acting are balanced with its actual benefits. I will give you that terroristic attacks are most costly not because of human lived but because of, well, spreading terror. I we could all see the threats as relatively minor to other threats, maybe their effects would be diminished. I think that they would loose their effect if they become common enough, because people get used to them and continue their lived, same way people continue their lives in war zones.Then, the precieved risk(or at least, the fear of this risk) would be smaller even if the risk itself would be higher.