In Britain, "tweedy" has evolved further from the definition given in AWAD ("Academic or scholarly; Informal; casual; outdoorsy"), and now has quite negative connotations. When applied to academics it presents an image that they are stuffy; outdated or old-fashioned; insulated from the harsh reality of the world outside. There may be some truth in this, for certain individuals...but there's no denying that much of it is grounded in the fairly widespread attitude of contempt for learning. (Oddly, Britain seems to be the only country in the world where calling someone "clever" is regarded as insulting them).