I fail to see how referendums are any more divisive than elections.
Does any party stick to it's manifest when elected. Lying and distortion are the stock in trade of all politicians. Catelonia may or may not become an issue for the EU prior to brexit. The EU was happy to break up Yugoslavia so their hypocrisy concerning Catelonia is quite blatant. If the hamfisted diplomacy of the EU continues I suspect the Basques and a few others will start making waves. The Catelonian referendum could simply have been allowed and then ignored. Magnifying it into a major issue has done nothing to further the cause of european unity.