a matador
Note from Walter Sickert, a Chapter from Anecdotes about 19th Century Authors Born After 1829

This means 'Bull-Fighter' whereas the author clearly means 'trouble-maker'.

The next two sentences

"I do not think that Lewis enjoyed this scintillation. (It did not seem to him to come from the right quarter.)"

also require interpretation and mean:

'Lewis was confused and surprised at becoming the target for innuendo.'