Yes, it could be attacked by both SM-2 and SM-6 at this stage. Whether they could succeed in intercepting the DF-21D is another matter. Your point is what, exactly? And where's that "demonstration" of an impenetrable ionized plasma shield surrounding a reentering DF-21D, or are you content to acknowledge that this is just coming out of your mouth and nowhere else?
You see his tactic again. Shifting goals after running out of arguments of "absolute plasma shield". Now he is using one of other absurdities, that is "absolute 100% guaranteed evasion of SM-2 and SM-6". As 100% only exist in theory but never in real world, SB is surely "invincible" but only on paper.
That way of thinking is equal to religious faith, not scientific because scientific method reject absolute sure thinking. A scientific rational person will say "according to what I know of, I believe ABC, that what-I-know of is only one of the possibilities of the truth. I believe what I know but I am also open to other possibilities and willing to be proven wrong". I am afraid that there are many religious "Engineers" and "Scientists" in the world who treat their knowledge and conclusion as God rather than one of many achievements/step stones towards the final truth which human can only get infinitely close but never be exact there.
BTW, the other thread he was schooled is the "China space program" thread, where he was told by me about the recent test of down-sized new generation space capsule on board LM-7. It successfully demonstrated the ability of maintaining communication through out the whole plasma period by exactly the method SB rejected on the ground of size. Again, he just refuse to face the fact and reality and hoped people in this thread will ignore that fact as he chose to. Some facts about the new reentry vehicle, height 2.3m, max diameter 2.6m, able to maintain communication through plasma period. DF-21 and DF-6 are 1.4m in diameter. It is very plausible that DF-21's warhead does the same if downsizing from a space shuttle to a 2.6m RV works. It is also very likely that the ASBM's warhead enters the atmosphere tail first during the plasma period and flip 180 degrees after deceleration for terminal guidance.
Regarding the efficiency of SM-2 and SM-6 against a warhead traveling at March "5-6", SB should think about P-700 and P-800 which travel below March 3. If those two are considered credible, then a March 6 ASBM is deadly.