Again, more astute-ness.

I didn't even know the law existed (it was passed in 2007 apparently), but of course, I didn't tell him that.
Of course, ignorance is no excuse. However, I have researched it (and I wouldn't think I could win but for that...), and the way I'm reading this law, it gives me the option to simply slow down if it is unsafe to change lanes (which is what I'm saying). I
did slow down, to 35 (posted speed limit there was 65), however, the law here makes no reference to a numerical amount, simply stating that it should be slow enough that you can be prepared to stop if necessary (which I think 35 would qualify).
I have spoken with the officer, and he doesn't think I slowed down that much. I'm not sure his basis for that assertion, except that he said he didn't see brake lights when I passed him. That seems like a shaky argument to me (I generally coast to slow down due to the fact that I drive a standard transmission car). Anyway, it boils down to my word against his, which is bad news in court generally...

Here's the actual text of the law in question. Note that I had to find this myself; the ticket makes no reference to a law that I'm charged under. Emphasis mine, of course:
§ 63-3-809. Procedure upon approach of authorized emergency vehicles; duty of driver of emergency vehicle.
(1) Upon the immediate approach of an authorized emergency vehicle, when the driver is giving audible signal by siren, exhaust whistle, or bell, the driver of every other vehicle shall yield the right-of-way and shall immediately drive to a position parallel to, and as close as possible to, the right-hand edge or curb of the roadway clear of any intersection and shall stop and remain in such position until the authorized emergency vehicle has passed, except when otherwise directed by a law enforcement officer.
(2) Upon approaching a stationary authorized emergency vehicle, when such vehicle is giving a signal by use of flashing, blinking, oscillating or rotating lights, as authorized under Section 63-7-19, a person who drives an approaching vehicle shall:
(a) Proceeding with due caution, yield the right-of-way by making a lane change into a lane not adjacent to that of the authorized emergency vehicle, if possible with due regard to safety and traffic conditions, if on a roadway having at least four (4) lanes with not less than two (2) lanes proceeding in the same direction as the approaching vehicle; or
(b) Proceeding with due caution, reduce the speed of the vehicle, maintaining a safe speed for road conditions and being prepared to stop, if changing lanes would be impossible or unsafe. (3) Upon approaching a stationary recovery vehicle or a highway maintenance vehicle, when such vehicle is giving a signal by use of authorized flashing lights, a person who drives an approaching vehicle shall:
(a) Proceeding with due caution, yield the right-of-way by making a lane change into a lane not adjacent to the stationary recovery vehicle or the highway maintenance vehicle, if possible with due regard to safety and traffic conditions, if on a roadway having at least four (4) lanes with not less than two (2) lanes proceeding in the same direction as the approaching vehicle; or
(b) Proceeding with due caution, reduce the speed of the vehicle, maintaining a safe speed for road conditions and being prepared to stop, if changing lanes would be impossible or unsafe.
(4) For purposes of this section, unless the context otherwise clearly requires:
(a) "Highway maintenance vehicle" means a vehicle used for the maintenance of highways and roadways in this state and is:
(i) Owned or operated by the Department of Transportation, a county, a municipality or other political subdivision of this state; or
(ii) Owned or operated by a contractor under contract with the Department of Transportation, a county, a municipality or other political subdivision of this state;
(b) "Recovery vehicle" means a truck that is specifically designed for towing a disabled vehicle or a combination of vehicles.
(5) A violation of this section is a misdemeanor punishable by a fine:
(a) Of not more than Two Hundred Fifty Dollars ($250.00); or
(b) Of not more than One Thousand Dollars ($1,000.00) if violation of this section results in:
(i) Property damage to the emergency vehicle, highway maintenance vehicle or recovery vehicle; or
(ii) Bodily injury to the driver or a passenger of any such vehicle.
(6) This section shall not operate to relieve the driver of an authorized emergency vehicle, a recovery vehicle or a highway maintenance vehicle from the duty to drive with due regard for the safety of all persons using the roadway.
Sources: Codes, 1942, § 8199; Laws, 1938, ch. 200; Laws, 2007, ch. 315, § 1, eff from and after July 1, 2007.