Gillow was somewhat OTT - by late 18th C apart from a few bigots Catholics were tolerated + could organise worship but finances precluded building churches + having full time priests on Island, hence when a priest was to come to Ramsey word would be sent to the outlying parishes - the law did however forbid marriage outside of an established church (this was only changed in 1849 - before this you can find a couple marrying in a CofE church and then a roman Catholic marriage same or next day) - likewise the CofE owned all burial grounds tho some vicars were it seems tolerant of catholic graveside services others were not (they also had regard for their fees!). The last outburst of anticatholic feelings came with the re-establishment of the catholic dioceses in the 1850's - this provoked troubles in England as well as a disturbance in Douglas (I keep meaning to transcribe a hilarious letter condemning it signed by nearly all the Manx Clergy at Convocation, apparently the CofE was in imminent danger of collapse if allowed - how things have changed now and Monsignor in full cassock has his place on the mound at Tynwald! along with Methodist + Salvation Army leaders)
In mid 18th C there were it seems quite a number of Irish Catholics involved with smuggling trade (they often had better boats + access to more capital than the Manx) - George Moore was irked at their success, his brother was a real bigot (even more than George who was not, it seems, the nicest of men) and stirred up trouble - judging from the accounts in Lib Scacc there were quite a number of Manx who had some regard for catholic priests (maybe old Catholicism, maybe just fishermen's superstitions - even in 1650's when Lord Derby took over a band of Manx to fight they were described as Papist by the parliamentarians and Catholic ways seemed to have survived in many parishes until early 18th C.