I would agree that finding spelling and grammatical errors can be off-putting and detracts from the intended message. However, it is important to recognise that in a person’s haste and excitement to get their point across and keep up with the conversation, they may not place as much importance in proofing their posts.
Spelling and grammar checking tools are not fool-proof and over-reliance on them can be detrimental to people’s language skills (which may be part of the problem).
In addition, other factors such as levels of literacy, English being a second language, or learning disabilities (for example dyslexia) can impede people’s effectiveness when attempting to communicate in writing. This should not undermine the fact that they may have very important and thought-provoking contributions to make.
It is worth considering the fact that in a world which discriminates and excludes on a regular basis, we could all do with striving to be more tolerant and open to other ways of thinking, no matter how at odds with our own beliefs they may be.