To force Catherine out of his home on a Sunday and making her travel unattended is so downright rude that it can't justified even by his belief that the Morlands were deceitful gold diggers.

However, I agree he had reasons to be angry (as long as John Thorpe is thought to be a believable source), as not only Catherine's fortune but her honour too was called into question. On less forgiving note, he should have considered Catherine's behaviour and how she had never hinted at being an heiress; Thorpe had been the only one to say that. In this manner he might have come to question how trustworthy John Thorpe was and made his own diligences to obtain definite information on the matter (as he did later regarding the matter of Mr Allen's heir).