Mryntu

I have somewhere the following sentence:

our platform negates the need for a middleman ...

but I do not want to offend or upset the middlemen whomever it is ... there are many middlemen in the context I'm reffering to there.

The question is how can I replace "negate" that is too abrupt, radical and may upset people with something more reasonable?

Would "diminishes" be a good alternative? other suggestions?

A (somewhat formal/technical) term used in such situations is obviate.

our platform obviates the need for a middleman ...

ODO:

obviate
VERB [WITH OBJECT]
1 Remove (a need or difficulty)

‘the presence of roller blinds obviated the need for curtains’

I'm in IT development, where our raison d'etre is to automate business processes which often put some people out of job. The standard approach we use to sell IT projects when we cannot outright eliminate the jobs is to empower them to do more value-added service to the business because with automation they have more time to do so.

I don't know your situation. If the middleman can be re-purposed you can say "our platform frees the middleman from administrative duties to empower them for ..."

EDIT: I didn't notice that Elliot already suggested the same thing.

I'd say:
Our platform allows you to forgo the middleman.
(Positive language, as opposed to negative.)

For one, I'd say if the need is only diminished then the platform has does not do the whole job. You are only ending the Need for the middleman. You are not taking them away and chopping them up. There are surely better things for them to go and do.

For alternatives you could use "Removes" or "Eliminates" the need. If you hope to be very gentle you could "relieve" the need for the middleman but that would be an odd choice.

Or get around it by "replacing" the middleman or 'Doing the job of the middleman'. In any case you are selling a function or product. It's impact on individuals is not part of the design or construction of the item.