What's a word to describe how someone talks differently to someone who's disabled?
Solution 1:
The person is talking and acting officiously. From The Free Dictionary:
officiously -- in an officious manner.
Officious
Marked by excessive eagerness in offering unwanted services or advice to others: an officious host; officious attention
The OP specifies that Person A is offering reassurance to Person B "even if Person B doesn't need the reassurance." The OP also specifies that this is done "with no malicious intent."
Person A will claim that he is "just trying to make Person B feel good" or "just trying to help"; what he is actually doing is insisting that he knows better than Person A does what Person A needs and wants. He is treating Person A like a child. This may be totally without malice, but it is officious.
Solution 2:
In response to the question of how to describe "one who talks differently to someone who is disabled"...to explain.."why being differently abled has its benefits to make them feel special"
insensitive
Showing or feeling no concern for others' feelings. ‘an insensitive remark’
-Oxford Dictionary Online
Going even further would be...
indifferent
3b : marked by a lack of interest, enthusiasm, or concern for something : apathetic indifferent to suffering and poverty
-Merriam Webster
Normally, during empathy training, we explain the concept in terms of "walking in another person´s shoes"; however, when the other person cannot even walk...the metaphor is useless.
Solution 3:
Infantilize [in-fuh n-tl-ahyz, -tahy-lahyz, in-fan-tl-ahyz] /verb (used with object), infantilized, infantilizing.
to keep in or reduce to an infantile state.
to treat or regard as infantile or immature.
If your intention is to demonstrate that Person B is reducing the integrity of Person A this might be a good term. It implies that Person B believes that Person A needs their additional support because the condition diminishes them to less than a capable person and therefore they need extra caring for.