All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.
Before answering your question, we would like to draw your attention to two important points:
Firstly, one should not engage in debates with the heretics unless he has adequate knowledge enabling him to refute their misconceptions and establish the evidence against them. It seems that you have not yet acquired the knowledge and ability to qualify you to do so. Hence, it is advisable that you strive in seeking knowledge until you acquire adequate knowledge and ability to engage in debate.
Secondly, experiencing such whisperings and evil thoughts may be a trial for the person. When the person repels and wards off such whisperings and evil thoughts, it is an indication of his strong faith. Shaykhul-Islam Ibn Taymiyyah wrote:
"The believer would be frequently put to trial by some signs of hypocrisy, and then Allaah would bless him with repentance; some may be plagued with spiritual diseases and acts entailing labeling them as hypocrites, but Allaah would repel such evil from them. The believer may be put to trial by satanic whisperings and insinuating thoughts of disbelief, which may make him feel distressed. The companions used to say, 'Oh Messenger of Allaah! Some of us would think thoughts that it is better for us to fall from the sky than speak of them.' He said, 'That is true faith.' [Ahmad and Muslim] Another version of the hadeeth reads, '…thoughts which are too terrible to speak of.' He said, 'Praise be to Allaah, Who has reduced all his [Satan’s] plots to mere whispers,' meaning that the fact that these whispers come, but they are so greatly disliked, and they are pushed away from the heart, is a clear sign of faith..." [Al-Fataawa]
We would like to warn you of indulging in thinking over such satanic whisperings; you should know that the best remedy for them is to totally ignore them. For more benefit, please refer to 199253.
As for the refutation of the misconception, your answer was correct. This point was underlined by Shaykh Ibn ʻUthaymeen as he wrote:
"The criterion in negation is to negate the following with respect to Allaah:
Firstly, all defects such as blindness, muteness, deafness, sleep, death... and the like.
Secondly, all imperfections such as imperfection pertaining to His Life, Knowledge, Ability, Greatness, Wisdom ... and the like.
Thirdly, any resemblance with His creation, suggesting that His Knowledge or Face is like those of His creation or that His istiwaa’ (mounting the Throne) is similar to that of the created ... and the like.
Among the evidence supporting the negation of the first category is the verse that reads (what means): {... and for Allaah is the highest attribute... } [Quran 16:60] The affirmation of ascribing the "highest attribute" to Him entails negation of all defects.
Among the evidence supporting the second category is the verse that reads (what means): {And We did certainly create the heavens and earth and what is between them in six days, and there touched Us no weariness.} [Quran 50:.38]
Among the evidence supporting the third category, Allaah, The Exalted, says (what means): {...There is nothing like unto Him...} [Quran 42:11]." [Taqreeb At-Tadmuriyyah]
Allaah knows best.