If everything has a purpose then evil doesn't exist

[R-Farmer]

1. “you are ignorant or stupid” is not an ad hominem attack.   it is an observation or assertion.

from the merrium-webster:
ad hominem
1 of 2
adjective
ad ho·mi·nem (ˈ)ad-ˈhä-mə-ˌnem  
-nəm
1
: appealing to feelings or prejudices rather than intellect
an ad hominem argument
2
: marked by or being an attack on an opponent's character rather than by an answer to the contentions made
made an ad hominem personal attack on his rival

So what makes what you did an ad hom attack was to address my personal deficiencies as you see them rather than address the content of my posting.

If We were discussing why the sky is blue and I give out some ludicrous explanation, Then to call be stupid for being wrong is an ad hom attack. Wether I am wrong or not is irrelevant. In an intelligent logic based discussion you can demonstrate how wrong your opponent/stupid your opponent is by besting him with in the contents of the discussion. by offering him proof, verifiable truth, logic or even a plausible theory. But the moment you go after the faults of an individual you abandon the intellectual discussion and concede the subject for an attack against the person. Which is what ad hominem means.

2. “you are wrong because your arguments do not make sense and contradict known facts” is not an ad hominem attack.  it is also an observation or assertion.

If my argument contains failures of logic then they should be easily dispelled with a citation to an authoritative source., verifiable truth, logic or even a plausible theory.  Calling someone 'stoo-ped' because you do not understand (which is what "makes no sense" actually means) is an appeal to a ad hom fallacy. Meaning you are attempting to win the argument without addressing the argument itself. If you do not understand someone how how it makes sense just ask a question. I am very happy to share and connect any missed dots. 

3. “you are wrong because your arguments do not make sense and contradict known facts, and you must be very ignorant or stupid to get it so wrong ” is also not an ad hominem attack.  it is also an observation, followed by a explanatory hypothesis.   the fact that the explanatory hypothesis is not flattering does not make it as hominem.

If your "explanatory hypothesis" focus on the messenger and not the content of the message it is an ad hom attack. Which in of itself is in fact a logical fallacy.

4. “you are wrong because you are ignorant and stupid” is an ad hominem attack. 

actually both are.