I think the idea is meant to more be that if you disagree enough to leave a reaction, actually type out why you disagree. It promotes discussion/debate and makes people actually think over why they have a differing opinion, rather than just knee-jerk tapping an on-screen button.
As I have stated before, we have no shortage of members willing to engage in debate via text, please point me to a thread with almost no text responses but hundreds of emoji responses. This simply doesn't happen. That being said if you post for the first time in a thread on page 8 of responses, yes, you might be receiving more emoji than text. The reason for this is that you were simply late to the party.
Given that, the only other reasons I can think of for removing disagree are:
1) Trolls - They will always exist, don't let them win, there are precious few of them.
2) Red thumbs and faces are far too triggering for those that need constant affirmations.
3) The need to know why (someone disagreed with you). It still boggles my mind that people care so much about a reaction from a random, anonymous person on the internet. If you feel that "text/words are better" just ignore the emoji... or can't you?
Reasons people might leave emoji disagreements:
1) English is not their primary language and they aren't comfortable enough to articulate an written argument.
2) Members might not be outgoing enough or confident enough to express a written opinion.
3) Accessibility, perhaps some members have a disability that makes it difficult to tedious to write a response but they still want to participate.
4) We are on page 10 of a thread and most ideas have been flushed out but you still want to register a vote without posting +1 or me too responses.
5) No time to write anything out but you still want to participate/register a vote. No different than a poll.