maybe because they can be used for many nefarious purposes?
You shouldn't ban general purpose technology because of particular bad uses.
Neither do "most US residents".
More to the point, your focus on guns is missing the larger point. There is very real and immediate dissatisfaction with the EU regulatory landscape. See: Brexit.
And in this case, the proposed regulation is:
“””[R]adio equipment [shall support] certain features in order to ensure that software can only be loaded into the radio equipment where the compliance of the combination of the radio equipment and software has been demonstrated.”””
Now I don’t think that’s a well written rule, but my problem is the specifics rather than the general idea. I think that either all broadcasts should be digitally signed, or it should not be possible for hackers to remotely modify many other people’s radios to broadcast false signals. (One-on-one modifications I don’t care about so much, but how do you write/pass such rules, given the difficulty getting people to care about or believe the scale difference between automated and manual hacking?)
In general, current regulation makes the owner of the equipment responsible for the broadcast.
This new regulation will just stifle development on SDR technologies
What situation? What crisis is happening I'm completely missing?
Imagine how ridiculous it would be to have a regulation on wheels that they must try to prevent being installed on non-approved devices.