The only thing different about drones is that they are slow and hence easier seen.
No, absolutely not! Motion is much easier to see. Consider a deer; hard to spot when it's standing still, much easier once it starts moving.
The easiest way spot other aircraft when I'm flying (did I mention I'm a student pilot?) is because of their apparent motion against a (usually contrasting) background. When birds or other aircraft are at the same altitude as me they appear just about on the horizon, and they're much harder to spot. Even gliders with 15-18 meter wingspans are tough to spot when they're at the same altitude - in fact, head-on collisions is a big safety issue that can even trip up top glider pilots (http://www.flarm.com/news/presscoverage/SSA_MainArticle_201405.pdf - the description on page 1 is particularly enlightening, and the graphic on page 3 shows the relative size of gliders relative to the time left to react). Drones are small and seeing one directly in front of me would NOT be easy.
There is zero new risk here and history shows that there is zero actual risk in this as nobody ever brought down a commercial airliner with a model airplane or helicopter. AFAIK it has not even been tried, ever.
The problem with this argument is that traditional model aircraft pilots didn't have cameras on their planes/helis. Now that drones come with them pre-installed, their pilots can fly at much longer range and without direct line of sight - traditional model aircraft pilots need to constantly watch their aircraft to keep it under control. Imagine the difficulty of hitting a target when your R/C heli is a few hundred feet away. Then imagine using an onboard camera to watch your target approach.
Now if you'd said that laws wouldn't prevent a terrorist from doing this, I'd agree with you. If you'd said that an outright ban on drones is unreasonable and untenable, I'd agree with you. I'd have even agreed if you'd said that the chances are slim of a terrorist actually using a drone maliciously. Where I strongly disagree is saying that the threat level hasn't changed. Technology has made drones more readily accessible and easier to pilot in a malicious manner, one need only look at the increased reports of near misses to realize that the number of drones being flown recklessly is increasing.